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QuickTime File Format

2001-03-01

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Contents

Introduction About This Document 13

Conventions Used in This Document 13
Special Fonts 14
Types of Notes 14
Updates to This Book 14
For More Information 14

Chapter 1 Introduction to Atoms 17

Atoms 17
Atom Layout 18
Atom Structure 19
QT Atoms 20
QT Atom Containers 22
Overview of the File Format 24
Free Space Atoms 25
Movie Data Atoms 26
Preview Atoms 26

Chapter 2 Movie Atoms 29

Overview of Movie Atoms 29
The Movie Atom 31
Movie Header Atoms 33
Color Table Atoms 35
User Data Atoms 36
Track Atoms 40
Track Header Atoms 41
Clipping Atoms 44
Clipping Region Atoms 45
Track Matte Atoms 45
Compressed Matte Atoms 46
Edit Atoms 47
Edit List Atoms 48
Track Load Settings Atoms 49
Track Reference Atoms 51
Track Input Map Atoms 53

3
2001-03-01 | © 2002, 2001 Apple Computer, Inc. All Rights Reserved.

C O N T E N T S

Media Atoms 56
Media Header Atoms 57
Handler Reference Atoms 58
Media Information Atoms 60
Video Media Information Atoms 60
Video Media Information Header Atoms 61
Sound Media Information Atoms 62
Sound Media Information Header Atoms 63
Base Media Information Atoms 64
Base Media Information Header Atoms 65
Base Media Info Atoms 65
Data Information Atoms 66
Data Reference Atoms 68
Sample Atoms 69
Sample Table Atoms 70
Sample Description Atoms 72
Time-to-Sample Atoms 73
Sync Sample Atoms 75
Sample-to-Chunk Atoms 77
Sample Size Atoms 79
Chunk Offset Atoms 80
Using Sample Atoms 82
Compressed Movie Resources 83
Allowing QuickTime to Compress the Movie Resource 83
Structure of a Compressed Movie Resource 83
Reference Movies 84
Reference Movie Atom 85
Reference Movie Descriptor Atom 86
Data Reference Atom 87
Data Rate Atom 88
CPU Speed Atom 88
Version Check Atom 89
Component Detect Atom 90
Constants 91
Quality Atom 92

Chapter 3 Media Data Atom Types 93

Video Media 94
Video Sample Description 94
Video Sample Data 96
Sound Media 101
Sound Sample Description 102
Sound Sample Data 104
Sound Codec Formats Supported 104
Uncompressed 8-Bit Sound 106

4

C O N T E N T S

Uncompressed 16-Bit Sound 106
IMA, uLaw, and aLaw 106
Floating-Point Formats 107
24- and 32-Bit Integer Formats 107
kMicrosoftADPCMFormat and kDVIIntelIMAFormat Sound Codecs 107
kDVAudioFormat Sound Codec 107
kQDesignCompression Sound Codec 107
MPEG Layer 3 (MP3) Codecs 108
Formats Not Currently in Use:MACE 3:1 and 6:1 108
Timecode Media 108
Timecode Sample Description 108
Timecode Media Information Atom 109
Text Media 111
Text Sample Description 111
Text Sample Data 113
Hypertext 114
Music Media 115
Music Sample Description 115
Music Sample Data 115
MPEG Media 115
MPEG Sample Description 115
MPEG Sample Data 115
Sprite Media 116
Sprite Sample Description 116
Sprite Sample Data 116
Sprite Track Properties 118
Sprite Track Media Format 119
Sprite Media Format Atoms 121
Sprite Media Format Extensions 121
Sprite Track Property Atoms 121
Atom Types 122
Sprite Button Behaviors 126
QT Atom Container Description Key 127
Sprite Media Handler Track Properties QT Atom Container Format 128
Sprite Media Handler Sample QT Atom Container Formats 128
Wired Action Grammar 129
Flash Media 135
Tween Media 136
Tween Sample Description 136
Tween Sample Data 136
Tween Type Categories 138
Tween QT Atom Container 138
Modifier Tracks 145
Limitations of Spatial Modifier Tracks 145
Track References 146
Chapter Lists 146

5

C O N T E N T S

3D Media 147
3D Sample Description 147
3D Sample Data 147
Streaming Media 147
Streaming Media Sample Description 148
Hint Media 148
Adding Hint Tracks to a Movie 149
Packetization Hint Media Header Atom 150
Hint Track User Data Atom 150
Movie Hint Info Atom 151
Finding an Original Media Track From a Hint Track 152
RTP Hint Tracks 152
Hint Sample Data Format 153
Packetization Hint Sample Data for Data Format 'rtp ' 155
No-Op Data Mode 159
Immediate Data Mode 160
Sample Mode 160
Sample Description Mode 162
VR Media 163
VR World Atom Container 164
Node Parent Atom 167
Node Location Atom Structure 167
Custom Cursor Atoms 168
Node Information Atom Container 169
Node Header Atom Structure 169
Hot Spot Parent Atom 170
Hot Spot Information Atom 171
Specific Information Atoms 172
Link Hot Spot Atom 172
URL Hot Spot Atom 175
Support for Wired Actions 175
QuickTime VR File Format 176
Single-Node Panoramic Movies 177
Single-Node Object Movies 177
Multinode Movies 178
QTVR Track 179
QuickTime VR Sample Description Structure 179
Panorama Tracks 180
Panorama Sample Atom Structure 180
Panorama Image Track 183
Cylindrical Panoramas 185
Cubic Panoramas 186
Image Tracks in Cubic Nodes 186
Panorama Tracks in Cubic Nodes 187
Nonstandard Cubes 188
Hot Spot Image Tracks 189

6

C O N T E N T S

Low-Resolution Image Tracks 189
Track Reference Entry Structure 189
Object Tracks 190
Object Sample Atom Structure 190
Track References for Object Tracks 196
Movie Media 197
Movie Sample Description 197
Movie Media Sample Format 197

Chapter 4 Basic Data Types 201

Language Code Values 201
Calendar Date and Time Values 203
Matrices 203
Graphics Modes 204
RGB Colors 206
Balance 206

Chapter 5 Some Useful Examples and Scenarios 207

Creating, Copying, and Disposing of Atom Containers 208
Creating New Atoms 208
Copying Existing Atoms 210
Retrieving Atoms From an Atom Container 211
Modifying Atoms 213
Removing Atoms From an Atom Container 214
Creating an Effect Description 215
Structure of an Effect Description 215
Required Atoms of an Effects Description 215
Parameter Atoms of an Effects Description 216
Creating an Input Map 217
Creating Movies With Modifier Tracks 220
Authoring Movies With External Movie Targets 221
Target Atoms for Embedded Movies 222
Adding Wired Actions To a Flash Track 222
Extending the SWF Format 223
Creating Video Tracks at 30 Frames-per-Second 225
Creating Video Tracks at 29.97 Frames-per-Second 225
Creating Audio Tracks at 44.1 Khz 226
Creating a Timecode Track for 29.97 FPS Video 226
Playing With Edit Lists 230
Interleaving Movie Data 232
Referencing Two Data Files With a Single Track 233
Getting the Name of a QuickTime VR Node 234
Adding Custom Atoms in a QuickTime VR Movie 236
Adding Atom Containers in a QuickTime VR Movie 237

7

C O N T E N T S

Optimizing QuickTime VR Movies for Web Playback 238
The QTVR Flattener 238
Sample Atom Container for the QTVR Flattener 239

Appendix A QuickTime Image File Format 241

Atom Types in QuickTime Image Files 241
Recommended File Type and Suffix 243

Appendix B Defining Media Data Layouts 245

Appendix C Random Access 247

Appendix D Meta-Data Handling 249

Digital Video File Formats 249
Digital Audio File Formats 250
Still Image File Formats 251
Animation and 3D File Formats 253

Appendix E Summary of VR World and Node Atom Types 255

C Summary 255
Constants 255
Data Types 257

Glossary 263

Index 271

8

Tables, Figures, and Listings

Chapter 1 Introduction to Atoms 17

Figure 1-1 A sample QuickTime atom 18
Figure 1-2 Calculating atom sizes 20
Figure 1-3 QT atom layout 21
Figure 1-4 QT atom container with parent and child atoms 22
Figure 1-5 A QT atom container with two child atoms 23
Figure 1-6 The structure of a QuickTime file 24
Figure 1-7 The layout of a preview atom 26
Table 1-1 Basic atom types of a QuickTime file 25

Chapter 2 Movie Atoms 29

Figure 2-1 Sample organization of a one-track video movie 31
Figure 2-2 The layout of a movie atom 32
Figure 2-3 The layout of a movie header atom 33
Figure 2-4 The layout of a color table atom 35
Figure 2-5 The layout of a user data atom 37
Figure 2-6 The layout of a track atom 40
Figure 2-7 The layout of a track header atom 42
Figure 2-8 The layout of a clipping atom 44
Figure 2-9 The layout of a track matte atom 46
Figure 2-10 The layout of an edit atom 48
Figure 2-11 The layout of an edit list table entry 49
Figure 2-12 The layout of a track load settings atom 50
Figure 2-13 The layout of a track reference atom 51
Figure 2-14 The layout of a track input map atom 53
Figure 2-15 The layout of a media atom 56
Figure 2-16 The layout of a media header atom 57
Figure 2-17 The layout of a handler reference atom 59
Figure 2-18 The layout of a media information atom for video 60
Figure 2-19 The layout of a media information header atom for video 61
Figure 2-20 The layout of a media information atom for sound 62
Figure 2-21 The layout of a sound media information header atom 63
Figure 2-22 The layout of a base media information atom 64
Figure 2-23 The layout of a base media info atom 65
Figure 2-24 The layout of a data information atom 67
Figure 2-25 Samples in a media 70

9

T A B L E S , F I G U R E S , A N D L I S T I N G S

Figure 2-26 The layout of a sample table atom 71
Figure 2-27 The layout of a sample description atom 72
Figure 2-28 The layout of a time-to-sample atom 74
Figure 2-29 The layout of a time-to-sample table entry 74
Figure 2-30 An example of a time-to-sample table 75
Figure 2-31 The layout of a sync sample atom 76
Figure 2-32 The layout of a sync sample table 76
Figure 2-33 The layout of a sample-to-chunk atom 77
Figure 2-34 The layout of a sample-to-chunk table entry 78
Figure 2-35 An example of a sample-to-chunk table 78
Figure 2-36 The layout of a sample size atom 79
Figure 2-37 An example of a sample size table 80
Figure 2-38 The layout of a chunk offset atom 81
Figure 2-39 An example of a chunk offset table 82
Figure 2-40 A movie atom containing a 'rmra' atom instead of a 'mvhd' atom 84
Figure 2-41 A ‘rmra’ atom with multiple ‘rmda’ atoms 86
Figure 2-42 Reference movie descriptor atom 87
Table 2-1 User data list entry types 38
Table 2-2 Track reference types 52
Table 2-3 Input types 55
Table 2-4 Data reference types 69
Table 2-5 Contents of complete compressed movie 84

Chapter 3 Media Data Atom Types 93

Figure 3-1 Motion-JPEG A dual-field sample data 100
Figure 3-2 Motion-JPEG B dual-field sample data 101
Figure 3-3 A key frame sample atom container 119
Figure 3-4 Atoms that describe a sprite and its properties 120
Figure 3-5 Atoms that describe sprite images 120
Figure 3-6 Structure of the VR world atom container 164
Figure 3-7 Structure of the node information atom container 169
Figure 3-8 The structure of a single-node panoramic movie file 177
Figure 3-9 The structure of a single-node object movie file 177
Figure 3-10 The structure of a multinode movie file 179
Figure 3-11 Creating an image track for a panorama 184
Figure 3-12 Creating an image track for a panorama, with the image track oriented horizontally
185
Figure 3-13 The structure of an image track for an object 196
Listing 3-1 Streaming media sample description 148
Table 3-1 Some image compression formats 94
Table 3-2 Video sample description extensions 96
Table 3-3 Supported QuickTime audio formats. Note that not all of these are uncompressed.
106
Table 3-4 Text sample extensions 114
Table 3-5 Sprite properties 117

10


Table 3-6 Sprite track properties 118
Table 3-7 Tween type values 137
Table 3-8 The 'hinf'atom type containing child atoms 152
Table 3-9 Hint track sample description 154
Table 3-10 The structure of table entries 155
Table 3-11 Fields and their special values as represented in the pano sample data atom,
providing backward compatibility to QuickTime VR 2.2 187
Table 3-12 Values for min and max fields 188
Table 3-13 Values used for representing six square sides 189

Chapter 4 Basic Data Types 201

Figure 4-1 How display matrices are used in QuickTime 204
Figure 4-2 Applying the transform 204
Table 4-1 QuickTime language code values 203
Table 4-2 QuickTime graphics modes 205

Chapter 5 Some Useful Examples and Scenarios 207

Figure 5-1 QT atom container after inserting an atom 209
Figure 5-2 QT atom container after inserting a second atom 209
Figure 5-3 Two QT atom containers, A and B 210
Figure 5-4 QT atom container after child atoms have been inserted 211
Figure 5-5 An example effect description for the Push effect 217
Figure 5-6 An example input map referencing two sources 219
Figure 5-7 Non-interleaved movie data 232
Figure 5-8 Interleaved movie data 232
Listing 5-1 Creating a new atom container 208
Listing 5-2 Disposing of an atom container 208
Listing 5-3 Creating a new QT atom container and calling QTInsertChild to add an atom.
208
Listing 5-4 Inserting a child atom 209
Listing 5-5 Inserting a container into another container 211
Listing 5-6 Finding a child atom by index 212
Listing 5-7 Finding a child atom by ID 212
Listing 5-8 Modifying an atom’s data 213
Listing 5-9 Removing atoms from a container 214
Listing 5-10 Adding a kParameterWhatName atom to the atom container effectDescription
216
Listing 5-11 Adding an input reference atom to an input map 219
Listing 5-12 Linking a modifier track to the track it modifies 220
Listing 5-13 Updating the input map 220
Listing 5-14 Getting a node’s name 235
Listing 5-15 Typical hot spot intercept procedure 236
Listing 5-16 Adding atom containers to a track 237
Listing 5-17 Using the flattener 238

11


Listing 5-18 Specifying a preview file for the flattener to use 239
Listing 5-19 Overriding the compression settings 240

Appendix A QuickTime Image File Format 241

Figure A-1 An 'idsc' atom followed by an 'idat' atom 242
Table A-1 A QuickTime image file containing JPEG-compressed data 242

12

I N T R O D U C T I O N

About This Document

This document, which supersedes the previous QuickTime File Format Specification, June, 2000, describes
the format and content of QuickTime files. It is current as of March, 2001, and is intended primarily
for developers who need to work with QuickTime files outside the context of the QuickTime
environment. For example, if you are developing a non-QuickTime application that imports QuickTime
files or works with QuickTime VR, you need to understand the material in this book.

QuickTime itself provides a number of high-level functions that you can use to create and manipulate
QuickTime files, without requiring you to understand the actual file format. These functions serve
to insulate developers from the low-level details of operation. But not all kinds of QuickTime files
can be created without the information presented here.

This document begins with an introduction to QuickTime atoms, then presents the structure of the
QuickTime file format in detail. This is followed by a series of code examples for manipulating a
QuickTime file using the QuickTime API. A series of appendixes describes some common file formats
that can be contained within a QuickTime file as data.

This document assumes that the reader is familiar with the basic concepts of digital video and digital
audio, as well as with QuickTime.

This book describes QuickTime files in general, rather than how they are supported on a specific
computing platform or in a specific programming language. As a result, the file format information
is presented in a tabular manner, rather than in coded data structures. Similarly, field names are
presented in English rather than as programming language tags. Furthermore, to the extent possible,
data types are described generically. For example, this book uses “32-bit signed integer” rather than
“long” to define a 32-bit integer value. Based on the information provided here, you should be able
to create appropriate data structure specifications for your environment.

QuickTime files are used to store QuickTime movies, as well as other time-based data. If you are
writing an application that parses QuickTime files, you should recognize that there may be non-movie
data in the files.

Important: The QuickTime file format has been used as the basis of the MPEG-4 standard, developed
by the International Organization for Standardization (ISO). s

Conventions Used in This Document

This document uses special conventions to present certain types of information.

Conventions Used in This Document 13

About This Document

Special Fonts
All code listings, reserved words, and the names of actual data structures, constants, fields, parameters,
and routines are shown in Letter Gothic (this is Letter Gothic).

Words that appear in boldface are key terms or concepts and are defined in the glossary.

Types of Notes
There are three types of notes used in this book.

Note: A note like this contains information that is interesting but possibly not essential to an
understanding of the main text.

Important: A note like this contains information that is essential for an understanding of the main
text.

Warning: A warning like this indicates potential problems that you should be aware of as you
design your application. Failure to heed these warnings could result in system crashes or loss
of data.

Updates to This Book

For any online updates to this book, check the QuickTime developers’ page on the World Wide Web
at

http://developer.apple.com/quicktime/

or you can go directly to the QuickTime New Documentation page at

http://developer.apple.com/documentation/Quicktime/QuickTime-rev-date.html

For More Information

For information about membership in Apple’s developer program, you should go to this URL:

http://devworld.apple.com/membership/

For technical support, go to this URL:

http://devworld.apple.com/products/techsupport/

For information on registering signatures, file types, and other technical information, contact

14 Updates to This Book

About This Document

Macintosh Developer Technical Support Apple Computer, Inc. 1 Infinite Loop, M/S 303-2T Cupertino,
CA 95014

For More Information 15

About This Document

16 For More Information

C H A P T E R 1

Introduction to Atoms

This chapter describes how QuickTime movies are stored on disk. The QuickTime file format is
designed to accommodate the various kinds of data that need to be stored in order to work with
digital media. Because the file format can be used to describe almost any media structure, it is an
ideal format for the exchange of digital media between applications, regardless of the platform on
which the application may be running.

A QuickTime file stores the description of the media separately from the media data. The description,
or meta-data, is called the movie and contains information such as the number of tracks, the video
compression format, and timing information. The movie also contains an index of where all the media
data is stored. The media data is all of the actual sample data, such as video frames and audio samples.
The media data may be stored in the same file as the QuickTime movie, in a separate file, or in several
files.

Before explaining the specifics of how a QuickTime movie is stored, it is important to first understand
the basic units that are used to construct QuickTime files. QuickTime uses two basic structures for
storing information: classic atoms and QT atoms. Both classic atoms, which are simple atoms, and
QT atoms, which are atom container atoms, allow you to construct arbitrarily complex hierarchical
data structures. Both also allow applications to ignore data they don’t understand.

QuickTime atom containers provide a basic structure for storing information in QuickTime. An atom
container is a tree-structured hierarchy of QT atoms.

Atoms

The basic data unit in a QuickTime file is the atom. Each atom contains size and type information
along with its data. The size field indicates the number of bytes in the atom, including the size and
type fields. The type field specifies the type of data stored in the atom and, by implication, the format
of that data.

Atom types are specified by a 32-bit integer, typically a four-character code. Apple Computer reserves
all four-character codes consisting entirely of lowercase letters. Unless otherwise stated, all data in a
QuickTime movie is stored in big-endian (network) byte ordering. All version fields must be set to
0, unless this document states otherwise.

Atoms 17

C H A P T E R 1

Atoms are hierarchical in nature. That is, one atom can contain one or more other atoms of varying
types. For example, a movie atom contains one track atom for each track in the movie. The track
atoms, in turn, contain one or more media atoms each, along with other atoms that define other track
and movie characteristics. This hierarchical structure of atoms is referred to as a containment hierarchy.

Classic atoms and QT atoms coexist within a single tree. Apple provides APIs that allow you to move
within a tree of QT atoms. With classic atoms, you read their size bytes and access their contents by
calculating offsets.

The format of the data stored within a given atom cannot be determined based only on the type field
of that atom. That is, an atom’s use is determined by its context. A given atom type can have different
usages when stored within atoms of different types. This means that all QuickTime file readers must
take into consideration not only the atom type, but also the atom’s containment hierarchy.

Atom Layout
Figure 1-1 (page 18) shows the layout of a sample QuickTime atom. Each atom carries its own size
and type information as well as its data. Throughout this document, the name of a container atom
(an atom that contains other atoms, including other container atoms) is printed in a gray box, and the
name of a leaf atom (an atom that contains no other atoms) is printed in a white box. Leaf atoms
contain data, usually in the form of tables.

Figure 1-1 A sample QuickTime atom

Container atom

Atom size
Atom type

Container atom

Atom size
Atom type

Leaf atom

Atom size
Atom type

Atom data

.
.
.

A leaf atom, as shown in Figure 1-1 (page 18), simply contains a series of data fields accessible by
offsets. You can use QuickTime’s atom tools to search through QT atom hierarchies until you get to
leaf atoms, then read the leaf atom’s data from its various fields.

Atoms within container atoms do not have to be in any particular order, with the exception of handler
description atoms. Handler description atoms must come before their data. For example, the media
handler description must come before a media information atom. A data handler description atom
must come before a data information atom.

18 Atoms

C H A P T E R 1

Atom Structure
Atoms consist of a header, followed by atom data. The header contains the atom’s size and type fields,
giving the size of the atom in bytes and its type. It may also contain an extended size field, giving the
size of a large atom as a 64-bit integer.

An atom header consists of the following fields.

Atom size
A 32-bit integer that indicates the size of the atom, including both the atom header and the
atom’s contents, including any contained atoms. Normally, the size field contains the actual
size of the atom, in bytes, expressed as a 32-bit unsigned integer. However, the size field can
contain special values that indicate an alternate method of determining the atom size. (These
special values are normally used only for media data ('mdat') atoms.) If the size field is set
to 0, which is allowed only for a top-level atom, this is the last atom in the file and it extends
to the end of the file. If the size field is set to 1, then the actual size is given in the extended
size field, an optional 64-bit field that follows the type field. This accomodates media data
atoms that contain more than 2^32 bytes. Figure 1-2 (page 20) shows how to calculate the size
of an atom.

Type
A 32-bit integer that contains the type of the atom. This can often be usefully treated as a
four-character field with a mnemonic value, such as 'moov' (0x6D6F6F76) for a movie atom,
or 'trak' (0x7472616B) for a track atom, but non-ASCII values (such as 0x00000001) are
also used. Knowing an atom's type allows you to interpret its data. An atom's data can be
arranged as any arbitrary collection of fields, tables, or other atoms. The data structure is
specific to the atom type. An atom of a given type has a defined data structure. If your
application encounters an atom of an unknown type, it should not attempt to interpret the
atom's data. Use the atom's size field to skip this atom and all of its contents. This allows a
degree of forward compatability with extensions to the QuickTime file format.

Extended Size
If the size field of an atom is set to 1, the type field is followed by a 64-bit extended size
field, which contains the actual size of the atom as a 64-bit unsigned integer. This is used when
the size of a media data atom exceeds 2^32 bytes.

When the size field contains the actual size of the atom, the extended size field is not present. This
means that when a QuickTime atom is modified by adding data, and its size crosses the 2^32 byte
limit, there is no extended size field in which to record the new atom size. Consequently, it is not
always possible to enlarge an atom beyond 2^32 bytes without copying its contents to a new atom.

To prevent this inconvenience, media data atoms are typically created with a 64-bit placeholder atom
immediately preceding them in the movie file. The placeholder atom has a type of
kWideAtomPlaceholderType ('wide'). Much like a 'free' or 'skip' atom, the 'wide' atom is
reserved space, but in this case the space is reserved for a specific purpose. If a 'wide' atom
immediately precedes a second atom, the second atom can be extended from a 32-bit size to a 64-bit
size simply by starting the atom header 8 bytes earlier (overwriting the 'wide' atom), setting the
size field to 1, and adding an extended size field. This way the offsets for sample data do not need
to be recalculated.

The 'wide' atom is exactly 8 bytes in size, and consists solely of its size and type fields. It contains
no other data.

Atoms 19

C H A P T E R 1

Note: A common error is thinking that the 'wide' atom contains the extended size. The 'wide' atom
is merely a placeholder that can be overwritten if necessary, by an atom header containing an extended
size field.

Figure 1-2 Calculating atom sizes

Implied

Size Size = 1 Size = 0

Type Type Type

Extended size
Size Size Size
( if size = 1)

End
of file

QT Atoms

Because of the limitations of the classic atom structure––that is, you need to know the offsets in order
to move through the atom tree––Apple created QT atoms. QT atoms are an enhanced data structure
that provide a more general-purpose storage format and remove some of the ambiguities that arise
when using simple atoms.

In particular, with classic atoms there is no way to know if an atom contains data or whether it contains
other atoms, or both, without specific knowledge about the atom. Using QT atoms, a given atom is
either a leaf atom or a container atom. There is no ambiguity. Furthermore, QT atoms allow for
multiple atoms of a given type to be specified through identification numbers. While QT atoms are
a more powerful data structure, they require more overhead in the file.

There are some advantages to using QT atoms for holding and passing information:

■ QT atoms can nest indefinitely, forming hierarchies that are easy to pass from one process to
another.
■ QuickTime provides a single set of tools by which you can search and manipulate QT atoms of
all types.

The QuickTime file format uses both classic atoms and QT atoms. In general, newer parts of the
QuickTime file format use QT atoms, while older parts use classic atoms. When defining new
QuickTime structures, you should use QT atoms whenever practical.

Figure 1-3 (page 21) depicts the layout of a QT atom. Each QT atom starts with a QT atom container
header, followed by the root atom. The root atom’s type is determined by the QT atom’s type. The
root atom contains any other atoms that are part of the structure.

Each container atom starts with a QT atom header followed by the atom’s contents. The contents are
either child atoms or data, but never both. If an atom contains children, it also contains all of its
children’s data and descendents. The root atom is always present and never has any siblings.

20 QT Atoms

C H A P T E R 1

Figure 1-3 QT atom layout

QT atom container header

Reserved
Lock count

QT atom header

Size
Type
Atom ID
Reserved
Child count
Reserved

Child atom

Size
Size
Type
Type

Child atom

Size
Size
Type
Type

A QT atom container header contains the following data.

Reserved
A 10-byte element that must be set to 0.

Lock count
A 16-bit integer that must be set to 0.

Each QT atom header contains the following data.

Size
A 32-bit integer that indicates the size of the atom in bytes, including both the QT atom header
and the atom’s contents. If the atom is a leaf atom, then this field contains the size of the single
atom. The size of container atoms includes all of the contained atoms. You can walk the atom
tree using the size and child count fields.

Type
A 32-bit integer that contains the type of the atom. If this is the root atom, the type value is set
to 'sean'.

QT Atoms 21

C H A P T E R 1

Atom ID
A 32-bit integer that contains the atom’s ID value. This value must be unique among its siblings.
The root atom always has an atom ID value of 1.

Reserved

Child count
A 16-bit integer that specifies the number of child atoms that an atom contains. This count only
includes immediate children. If this field is set to 0, the atom is a leaf atom and only contains
data.

Reserved

QT Atom Containers

A QuickTime atom container is a basic structure for storing information in QuickTime. An atom
container is a tree-structured hierarchy of QT atoms. You can think of a newly created QT atom
container as the root of a tree structure that contains no children.

A QT atom container contains QT atoms, as shown in Figure 1-4 (page 22). Each QT atom contains
either data or other atoms. If a QT atom contains other atoms, it is a parent atom and the atoms it
contains are its child atoms. Each parent’s child atom is uniquely identified by its atom type and atom
ID. A QT atom that contains data is called a leaf atom.

Figure 1-4 QT atom container with parent and child atoms

QT atom
container

Parent atom

Atom type Atom type

Atom ID Atom ID

Atom data
Child atoms

Atom type Atom type

Atom ID Atom ID

Atom data

Each QT atom has an offset that describes the atom’s position within the QT atom container. In
addition, each QT atom has a type and an ID. The atom type describes the kind of information the
atom represents. The atom ID is used to differentiate child atoms of the same type with the same

22 QT Atom Containers

C H A P T E R 1

parent; an atom’s ID must be unique for a given parent and type. In addition to the atom ID, each
atom has a 1-based index that describes its order relative to other child atoms of the same parent with
the same atom type. You can uniquely identify a QT atom in one of three ways:

■ by its offset within its QT atom container
■ by its parent atom, type, and index
■ by its parent atom, type, and ID

You can store and retrieve atoms in a QT atom container by index, ID, or both. For example, to use a
QT atom container as a dynamic array or tree structure, you can store and retrieve atoms by index.
To use a QT atom container as a database, you can store and retrieve atoms by ID. You can also create,
store, and retrieve atoms using both ID and index to create an arbitrarily complex, extensible data
structure.

Warning: Since QT atoms are offsets into a data structure, they can be changed during editing
operations on QT atom containers, such as inserting or deleting atoms. For a given atom, editing
child atoms is safe, but editing sibling or parent atoms invalidates that atom’s offset. s

Note: For cross-platform purposes, all data in a QT atom is expected to be in big-endian format.
However, leaf data can be little-endian if it is custom to an application. u

Figure 1-5 (page 23) shows a QT atom container that has two child atoms. The first child atom (offset
= 10) is a leaf atom that has an atom type of 'abcd', an ID of 1000, and an index of 1. The second child
atom (offset = 20) has an atom type of 'abcd', an ID of 900, and an index of 2. Because the two child
atoms have the same type, they must have different IDs. The second child atom is also a parent atom
of three atoms.

Figure 1-5 A QT atom container with two child atoms

QT atom
container

Index= 1 Index= 2
Offset= 10 Offset= 20

'abcd' 'abcd'
900
1000

Data
Index= 1 Index= 1 Index= 2
Offset= 30 Offset= 40 Offset= 50

'abcd' 'word' 'abcd'
100 100 1000

"Hello"

The first child atom (offset = 30) has an atom type of 'abcd', an ID of 100, and an index of 1. It does
not have any children, nor does it have data. The second child atom (offset = 40) has an atom type of
'word', an ID of 100, and an index of 1. The atom has data, so it is a leaf atom. The second atom (offset

QT Atom Containers 23

C H A P T E R 1

= 40) has the same ID as the first atom (offset = 30), but a different atom type. The third child atom
(offset = 50) has an atom type of 'abcd', an ID of 1000, and an index of 2. Its atom type and ID are
the same as that of another atom (offset = 10) with a different parent.

Note: If you are working with the QuickTime API, you do not need to parse QT atoms. Instead, the
QT atom functions can be used to create atom containers, add atoms to and remove atoms from atom
containers, search for atoms in atom containers, and retrieve data from atoms in atom containers.

Most QT atom functions take two parameters to specify a particular atom: the atom container that
contains the atom, and the offset of the atom in the atom container data structure. You obtain an
atom’s offset by calling either QTFindChildByID or QTFindChildByIndex. An atom’s offset may be
invalidated if the QT atom container that contains it is modified.

When calling any QT atom function for which you specify a parent atom as a parameter, you can
pass the constant kParentAtomIsContainer as an atom offset to indicate that the specified parent
atom is the atom container itself. For example, you would call the QTFindChildByIndex function and
pass kParentAtomIsContainer constant for the parent atom parameter to indicate that the requested
child atom is a child of the atom container itself.

Overview of the File Format

A QuickTime file is simply a collection of atoms. QuickTime does not impose any rules about the
order of these atoms.

Figure 1-6 (page 24) depicts a typical QuickTime file.

Figure 1-6 The structure of a QuickTime file

Bytes

Movie data atom

Atom size 4

Type = 'mdat' 4

Data Variable

.
.
.

Movie atom

Atom size 4

Type = 'moov' 4

Data Variable

24 Overview of the File Format

C H A P T E R 1

In file systems that support filename extensions, QuickTime filenames typically have an extension of
.mov. On the Macintosh platform, QuickTime files have a file type of 'MooV'. On the Macintosh, the
movie atom may be stored as a Macintosh resource using the Resource Manager. The resource has a
type of 'moov'. All media data is stored in the data fork. On the Internet, QuickTime files are served
under the mime type "video/quicktime".

As previously discussed, QuickTime files consist of atoms, each with an appropriate atom type. A
few of these types are considered basic atom types and form the structure within which the other
atoms are stored. Table 1-1 (page 25) lists the currently supported basic atom types.

Table 1-1 Basic atom types of a QuickTime file

Atom type Use

'free' Unused space available in file.

'skip' Unused space available in file.

'wide' Reserved space—can be overwritten by an extended size field.

'pnot' Reference to movie preview data.

'moov' Movie resource—meta-data about the movie (number and type of
tracks, location of sample data, and so on).

'mdat' Movie sample data—usually this data can be interpreted only by using
the movie resource.

Although it is true that QuickTime imposes no strict order on a movie’s atoms, it is often convenient
if the movie atom appears near the front of the file. For example, an application that plays a movie
over a network would not necessarily have access to the entire movie at all times. If the movie atom
is stored at the beginning of the file, the application can use the meta-data to understand the movie’s
content as it is acquired over the network. This can allow an application to play a movie as it
downloads.

The following sections, as well as Chapter 3, “Movie Atoms,” (page 29) describe each of these basic
atom types in more detail, including descriptions of the atoms that each basic atom may contain.

Free Space Atoms
Both free and skip atoms designate unused space in the movie data file. These atoms consist only of
an atom header (atom size and type fields), followed by the appropriate number of bytes of free space.
When reading a QuickTime movie, your application may safely skip these atoms. When writing or
updating a movie, you may reuse the space associated with these atom types. The wide atom consists
only of a type and size field. This occupies 8 bytes—enough space to add an extended size field to
the header of the atom that follows. If an atom grows to exceed 2^32 bytes in size, and it is preceded
by a wide atom, you may create a new atom header, containing an extended size field, by overwriting
the wide atom.


C H A P T E R 1

Movie Data Atoms
As with the free and skip atoms, the movie data atom is structured quite simply. It consists of an atom
header (atom size and type fields), followed by the movie’s media data. Your application can
understand the data in this atom only by using the meta-data stored in the movie atom. This atom
can be quite large, and may exceed 2^32 bytes, in which case the size field will be set to 1, and the
header will contain a 64-bit extended size field.

Preview Atoms
The preview atom contains information that allows you to find the preview image associated with a
QuickTime movie. The preview image, or poster, is a representative image suitable for display to the
user in, for example, Open dialog boxes. Figure 1-7 (page 26) depicts the layout of the preview atom.

Figure 1-7 The layout of a preview atom

Bytes

Preview atom

Atom size 4

Type = 'pnot' 4

Modification date 4

Version number 2

Atom type 4

Atom index 2

The preview atom has an atom type value of 'pnot' and, following its atom header, contains the
following fields.

Size
A 32-bit integer that specifies the number of bytes in this preview atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'pnot'.

Modification date
A 32-bit unsigned integer containing a date that indicates when the preview was last updated.
The data is in standard Macintosh format.

Version number

Atom type
A 32-bit integer that indicates the type of atom that contains the preview data. Typically, this
is set to 'PICT' to indicate a QuickDraw picture.


C H A P T E R 1

Atom index
A 16-bit integer that identifies which atom of the specified type is to be used as the preview.
Typically, this field is set to 1 to indicate that you should use the first atom of the type specified
in the atom type field.


C H A P T E R 1


C H A P T E R 2

Movie Atoms

This chapter provides a general introduction to QuickTime movie atoms, as well as specific details
on the layout and usage of these atoms.

If you are a QuickTime application or tool developer, you’ll want to read this chapter in order to
understand the characteristics and usage of QuickTime movie atoms. Each atom type discussed in
this chapter is shown with an accompanying illustration that contains offset information, followed
by field descriptions.

This chapter is divided into the following major sections:

■ “Overview of Movie Atoms” (page 29) discusses QuickTime movie atoms, which act as containers
for information that describes a movie’s data. A conceptual illustration is provided that shows
the organization of a simple, one-track QuickTime movie. Color table atoms and user data atoms
are also discussed.
■ “Track Atoms” (page 40) describes track atoms, which define a single track of a movie.
■ “Media Atoms” (page 56) discusses media atoms, which define a track’s movie data.
■ “Sample Atoms” (page 69) discusses how QuickTime stores media data in samples. The section
also includes examples of how you use these sample atoms.
■ “Compressed Movie Resources” (page 83) discusses compressed movie resources, in which a
lossless compression algorithm is used to compress the contents of the movie atom, including
any track, media, or sample atoms. the contents must be decompressed before the movie atom
can be parsed.
■ “Reference Movies” (page 84) discusses movies that contain a list of references to alternate movies,
as well as the criteria for selecting the correct movie from a list of alternates.

Overview of Movie Atoms

QuickTime movie atoms have an atom type of 'moov'. These atoms act as a container for the
information that describes a movie’s data. This information, or meta-data, is stored in a number of
different types of atoms. Generally speaking, only meta-data is stored in a movie atom. Sample data
for the movie, such as audio or video samples, are referenced in the movie atom, but are not contained
in it.


C H A P T E R 2
Movie Atoms

The movie atom is essentially a container of other atoms. These atoms, taken together, describe the
contents of a movie. At the highest level, movie atoms typically contain track atoms, which in turn
contain media atoms. At the lowest level you find the leaf atoms, which contain non-atom data,
usually in the form of a table or a set of data elements. For example, the track atom contains the edit
atom, which contains a leaf atom called the edit list atom. The edit list atom contains an edit list table.
Both of these atoms are discussed later in this book.

Figure 2-1 (page 31) provides a conceptual view of the organization of a simple, one-track QuickTime
movie. Each nested box in the illustration represents an atom that belongs to its parent atom. The
figure does not show the data regions of any of the atoms. These areas are described in the sections
that follow.

Note that this figure shows the organization of a standard movie atom. It is possible to compress the
movie meta-data using a lossless compression algorithm. In such cases, the movie atom contains only
a single child atom—the compressed movie atom ('cmov'). When this child atom is uncompressed,
its contents conform to the structure shown in the following illustration. For details, see “Compressed
Movie Resources”.

It is also possible to create a reference movie, a movie that refers to other movies; in this case the
movie atom may contain only a reference movie atom ('rmra'). For details, see “Reference Movies”.

It is even possible to construct a chain of reference movies, in which one reference movie points to
another, but ultimately the chain must end in either a standard movie atom, such as the one illustrated
below, or a compressed movie atom, which can be uncompressed to obtain the same structure.

30 Overview of Movie Atoms

C H A P T E R 2
Movie Atoms

Figure 2-1 Sample organization of a one-track video movie

Movie atom
Atom size
Type ='moov'
Movie clipping atom User data atom

Atom size Atom size
Type = 'clip' Type = 'udta'

Movie header atom Clipping region atom Movie user data

Atom size Atom size Atom size
Type = 'mvhd' Type = 'crgn' Type = User defined

Track atom
Atom size
Type ='trak'

Track clipping atom Track matte atom Edit atom

Atom size Atom size Atom size
Type = 'clip' Type = 'matt' Type = 'edts'

Track header atom Clipping region atom Compressed matte atom Edit list atom

Atom size Atom size Atom size Atom size
Type = 'tkhd' Type = 'crgn' Type = 'kmat' Type = 'elst'

Media atom
Atom size
Type ='mdia'
Media header atom Media handler reference atom

Atom size Atom size
Type = 'mdhd' Type = 'hdlr'

Video media information atom
Atom size
Type ='minf'
Data information atom
Atom size
Type = 'dinf'

Data reference atom
Atom size
Video media information Type = 'dref'
Data handler reference atom
header atom
.
Data references
.
Atom size
Type = 'vmhd'
Atom size
Type = 'hdlr'
.

Sample table atom

Time-to-sample atom
Atom size Sample-to-chunk atom
Type ='stbl'
Atom size Atom size
Type ='stts' Type = 'stsc'

Sync sample atom Sample description atom Sample size atom Chunk offset atom

Atom size Atom size Atom size Atom size
Type ='stss' Type = 'stsd' Type = 'stsz' Type = 'stco'

The Movie Atom
You use movie atoms to specify the information that defines a movie—that is, the information that
allows your application to understand the data that is stored in the movie data atom. The movie atom
normally contains a movie header atom, which defines the time scale and duration information for
the entire movie, as well as its display characteristics. In addition, the movie atom contains a track
atom for each track in the movie.

The movie atom has an atom type of 'moov'. It contains other types of atoms, including at least one
of three possible parent atoms—the movie header atom ('mvhd'), the compressed movie atom ('cmov'),
or a reference movie atom ('rmra'). An uncompressed movie atom can contain both a movie header


C H A P T E R 2
Movie Atoms

atom and a reference movie atom, but it must contain at least one of the two. It can also contain several
other atoms, such as a clipping atom ('clip'), one or more track atoms ('trak'), a color table atom
('ctab'), and a user data atom 'udta').

Compressed movie atoms and reference movie atoms are discussed separately. This section describes
normal uncompressed movie atoms.

Figure 2-2 (page 32) shows the layout of a typical movie atom.

Figure 2-2 The layout of a movie atom

Movie atom

Atom size
Type = 'moov'

Movie header atom 'mvhd'‡

Clipping atom 'clip'

One or more track atoms 'trak'

User data atom 'udta'

Color table atom 'ctab'

‡ Required atom

A movie atom may contain the following information.

Size
The number of bytes in this movie atom.

Type
The type of this movie atom; this field must be set to 'moov'.

Movie header atom
See “Movie Header Atoms” (page 33) for more information.

Movie clipping atom
See “Clipping Atoms” (page 44) for more information.

Track list atoms
See “Track Atoms” (page 40) for details on track atoms and their associated atoms.

User data atom
See “User Data Atoms” (page 36) for more infomation about user data atoms.

Color table atom
See “Color Table Atoms” (page 35) for a discussion of the color table atom.


C H A P T E R 2
Movie Atoms

Compressed movie atom
See “Compressed Movie Resources” for a discussion of compressed movie atoms.

Reference movie atom
See “Reference Movies” (page 84) for a discussion of reference movie atoms.

Movie Header Atoms
You use the movie header atom to specify the characteristics of an entire QuickTime movie. The data
contained in this atom defines characteristics of the entire QuickTime movie, such as time scale and
duration. It has an atom type value of 'mvhd'.

Figure 2-3 (page 33) shows the layout of the movie header atom. The movie header atom is a leaf
atom.

Figure 2-3 The layout of a movie header atom

Bytes

Movie header atom

Atom size 4

Type = 'mvhd' 4

Version 1

Flags 3

Creation time 4

Modification time 4

Time scale 4

Duration 4

Preferred rate 4

a Preferred volume 2
b
u a b u Reserved 10
c
d c d v Matrix structure 36
v
x x y w Preview time 4
y
w Preview duration 4

Poster time 4

Selection time 4

Selection duration 4

Current time 4

Next track ID 4


C H A P T E R 2
Movie Atoms

You define a movie header atom by specifying the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this movie header atom.

Type
A 32-bit integer that identifies the atom type; must be set to 'mvhd'.

Version
A 1-byte specification of the version of this movie header atom.

Flags
Three bytes of space for future movie header flags.

Creation time
A 32-bit integer that specifies (in seconds since midnight, January 1, 1904) when the movie
atom was created.

Modification time
A 32-bit integer that specifies (in seconds since midnight, January 1, 1904) when the movie
atom was changed.

Time scale
A time value that indicates the time scale for this movie—that is, the number of time units that
pass per second in its time coordinate system. A time coordinate system that measures time
in sixtieths of a second, for example, has a time scale of 60.

Duration
A time value that indicates the duration of the movie in time scale units. Note that this property
is derived from the movie’s tracks. The value of this field corresponds to the duration of the
longest track in the movie.

Preferred rate
A 32-bit fixed-point number that specifies the rate at which to play this movie. A value of 1.0
indicates normal rate.

Preferred volume
A 16-bit fixed-point number that specifies how loud to play this movie’s sound. A value of 1.0
indicates full volume.

Reserved
Ten bytes reserved for use by Apple. Set to 0.

Matrix structure
The matrix structure associated with this movie. A matrix shows how to map points from one
coordinate space into another. See “Matrices” (page 203) for a discussion of how display matrices
are used in QuickTime.


C H A P T E R 2
Movie Atoms

Preview time
The time value in the movie at which the preview begins.

Preview duration
The duration of the movie preview in movie time scale units.

Poster time
The time value of the time of the movie poster.

Selection time
The time value for the start time of the current selection.

Selection duration
The duration of the current selection in movie time scale units.

Current time
The time value for current time position within the movie.

Next track ID
A 32-bit integer that indicates a value to use for the track ID number of the next track added
to this movie. Note that 0 is not a valid track ID value.

Color Table Atoms
Color table atoms define a list of preferred colors for displaying the movie on devices that support
only 256 colors. The list may contain up to 256 colors. These optional atoms have a type value of
'ctab'. The color table atom contains a Macintosh color table data structure.

Figure 2-4 (page 35) shows the layout of the color table atom.

Figure 2-4 The layout of a color table atom

Color table atom Bytes

Atom size 4

Type = 'ctab' 4

Color table seed 4

Color table flags 2

Color table size 2

Color array n

The color table atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this color table atom.


C H A P T E R 2
Movie Atoms

Type
A 32-bit integer that identifies the atom type; this field must be set to 'ctab'.

Color table seed

Color table flags
A 16-bit integer that must be set to 0x8000.

Color table size
A 16-bit integer that indicates the number of colors in the following color array. This is a
zero-relative value; setting this field to 0 means that there is one color in the array.

Color array
An array of colors. Each color is made of four unsigned 16-bit integers. The first integer must
be set to 0, the second is the red value, the third is the green value, and the fourth is the blue
value.

User Data Atoms
User data atoms allow you to define and store data associated with a QuickTime object, such as a
movie, track, or media. This includes both information that QuickTime looks for, such as copyright
information or whether a movie should loop, and arbitrary information—provided by and for your
application—that QuickTime simply ignores.

A user data atom whose immediate parent is a movie atom contains data relevant to the movie as a
whole. A user data atom whose parent is a track atom contains information relevant to that specific
track. A QuickTime movie file may contain many user data atoms, but only one user data atom is
allowed as the immediate child of any given movie atom or track atom.

The user data atom has an atom type of 'udta'. Inside the user data atom is a list of atoms describing
each piece of user data. User data provides a simple way to extend what is stored in a QuickTime
movie. For example, you can use data atoms to store a movie’s window position, playback
characteristics, or creation information.

This section describes the data atoms that QuickTime recognizes. You may create new data atom
types that your own application recognizes. Applications should ignore any data atom types they do
not recognize.

Figure 2-5 (page 37) shows the layout of a user data atom.


C H A P T E R 2
Movie Atoms

Figure 2-5 The layout of a user data atom

Bytes
User data atom

Atom size 4

Type = 'udta' 4

User data list ‡

Atom size 4
Type = user data types 4

User data list

‡ Required atom

The user data atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this user data atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'udta'.

User data list
A user data list that is formatted as a series of atoms. Each data element in the user data list
contains size and type information along with its data. For historical reasons, the data list is
optionally terminated by a 32-bit integer set to 0. If you are writing a program to read user
data atoms, you should allow for the terminating 0. However, if you are writing a program to
create user data atoms, you can safely leave out the trailing 0.
Table 2-1 (page 37) lists the currently defined list entry types.

Table 2-1 User data list entry types

List entry
Description
type

'© cpy' Copyright statement.

'© day' Date the movie content was created.

'© dir' Name of movie’s director.

'© ed1' to Edit dates and descriptions.
'© ed9'

'© fmt' Indication of movie format (computer-generated, digitized, and so
on).


C H A P T E R 2
Movie Atoms

List entry
Description
type

'© inf' Information about the movie.

'© prd' Name of movie’s producer.

'© prf' Names of performers.

'© req' Special hardware and software requirements.

'© src' Credits for those who provided movie source content.

'© wrt' Name of movie’s writer.

'name' Name of object.

'WLOC' Default window location for movie. Two 16-bit values, {x,y}.

'LOOP' Long integer indicating looping style. This atom is not present unless
the movie is set to loop. Values are 0 for normal looping, 1 for
palindromic looping.

'SelO' Play selection only. Byte indicating that only the selected area of the
movie should be played.

'AllF' Play all frames. Byte indicating that all frames of video should be
played, regardless of timing.

'ptv ' Print to video. Display movie in full screen mode. This atom contains
a 16-byte structure, described in “Print to Video (Full Screen
Mode)” (page 39).

'hnti' Hint info atom. Data used for real-time streaming of a movie or a
track. For more information, see “Movie Hint Info Atom” (page 151)
and “Hint Track User Data Atom” (page 150).

'hinf' Hint track information. Statistical data for real-time streaming of a
particular track. For more information, see “Hint Track User Data
Atom” (page 150).

All user data list entries whose type begins with the © character (ASCII 169) are defined to be
international text. These list entries must contain a list of text strings with associated language codes.
By storing multiple versions of the same text, a single user data text item can contain translations for
different languages.

The list of text strings uses a small integer atom format, which is identical to the QuickTime atom
format, except that it uses 16-bit values for size and type instead of 32-bit values. The first value is
the size of the string, including the size and type, and the second value is the language code for the
string.


C H A P T E R 2
Movie Atoms

The window location, looping, play selection only, play all frames, and print to video atoms control
the way QuickTime displays a movie. These atoms are interpreted only if the user data atom’s
immediate parent is a movie atom ('moov'). If they are included as part of a track atom’s user data,
they are ignored.

Print to Video (Full Screen Mode)

A movie atom’s user data atom may contain a print to video atom ('ptv ') . If a print to video atom
is present, QuickTime plays the movie in full-screen mode, with no window and no visible controller.
Any portion of the screen not occupied by the movie is cleared to black. The user must press the esc
key to exit full-screen mode.

This atom is often added and removed transiently to control the display mode of a movie for a single
presentation, but it can also be stored as part of the permanent movie file.

The print to video atom consists of the following data.

Size
A 32-bit integer that specifies the number of bytes in this user data item.

Type
A 32-bit integer that identifies the item type; this field must be set to 'ptv '. Note that the
fourth character is an ASCII blank.

Display size
A 16-bit little-endian integer indicating the display size for the movie: 0 indicates that the movie
should be played at its normal size; 1 indicates that the movie should be played at double size;
2 indicates that the movie should be played at half size; 3 indicates that the movie should be
scaled to fill the screen; 4 indicates that the movie should be played at its current size (this last
value is normally used when the print to video atom is inserted transiently and the movie has
been temporarily resized).

Reserved1
A 16-bit integer whose value should be 0.

Reserved2
A 16-bit integer whose value should be 0.

Slide show
An 8-bit boolean whose value is 1 for a slide show. In slide show mode, the movie advances
one frame each time the right-arrow key is pressed. Audio is muted.

Play on open
An 8-bit boolean whose value is normally 1, indicating that the movie should play when
opened. Since there is no visible controller in full-screen mode, applications should always set
this field to 1 to prevent user confusion.


C H A P T E R 2
Movie Atoms

Track Atoms

Track atoms define a single track of a movie. A movie may consist of one or more tracks. Each track
is independent of the other tracks in the movie and carries its own temporal and spatial information.
Each track atom contains its associated media atom.

Tracks are used specifically for the following purposes:

■ To contain media data references and descriptions (media tracks).
■ To contain modifier tracks (tweens, and so forth).
■ To contain packetization information for streaming protocols (hint tracks). Hint tracks may contain
references to media sample data or copies of media sample data. For more information about
hint tracks, refer to “Hint Media” (page 148).

Note that a QuickTime movie cannot consist solely of hint tracks or modifier tracks; there must be at
least one media track. Furthermore, media tracks cannot be deleted from a hinted movie, even if the
hint tracks contain copies of the media sample data—in addition to the hint tracks, the entire unhinted
movie must remain.

Figure 2-6 (page 40) shows the layout of a track atom. Track atoms have an atom type value of 'trak'.
The track atom requires the track header atom ('tkhd') and the media atom ('mdia'). Other child
atoms are optional, and may include a track clipping atom ('clip'), a track matte atom ('matt'), an
edit atom ('edts'), a track reference atom ('tref'), a track load settings atom ('load'), a track input
map atom ('imap'), and a user data atom ('udta').

Figure 2-6 The layout of a track atom

Track atom

Atom size
Type = 'trak'

Track header atom 'tkhd' ‡


Track matte atom 'matt'

Edit atom 'edts'

Track reference atom 'tref'

Track loading settings atom 'load'

Track input map atom 'imap'

Media atom 'mdia' ‡

User-defined data atom 'udta'

‡ Required atom

Track atoms contain the following data elements.

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Size
A 32-bit integer that specifies the number of bytes in this track atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'trak'.

Track header atom
See “Track Header Atoms” (page 41) for details.

Clipping atom
See “Clipping Atoms” (page 44) for more information.

Track matte atom
See “Track Matte Atoms” (page 45) for more information.

Edit atom
See “Edit Atoms” (page 47) for details.

Track reference atom
See “Track Reference Atoms” (page 51)” for details.

Track load settings atom
See “Track Load Settings Atoms” (page 49) for details.

Track input map atom
See “Track Input Map Atoms” (page 53)” for details.

Media atom
See “Media Atoms” (page 56) for details.

User-defined data atom
See “User Data Atoms” (page 36) for more information.

Track Header Atoms
The track header atom specifies the characteristics of a single track within a movie. A track header
atom contains a size field that specifies the number of bytes and a type field that indicates the format
of the data (defined by the atom type 'tkhd').

Figure 2-7 (page 42) shows the structure of the track header atom.

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Figure 2-7 The layout of a track header atom

Bytes

Track header atom

Atom size 4

Type = 'tkhd' 4

Version 1

Flags 3

Creation time 4

Modification time 4

Track ID 4

Reserved 4

Duration 4

Reserved 8

Layer 2

Alternate group 2

Volume 2

Reserved 2

Matrix structure 36

Track width 4

Track height 4

The track header atom contains the track characteristics for the track, including temporal, spatial, and
volume information.

Track header atoms contain the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this track header atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'tkhd'.

Version
A 1-byte specification of the version of this track header.

Flags
Three bytes that are reserved for the track header flags. These flags indicate how the track is
used in the movie. The following flags are valid (all flags are enabled when set to 1).
Track enabled

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Indicates that the track is enabled. Flag value is 0x0001.

Track in movie

Indicates that the track is used in the movie. Flag value is 0x0002.

Track in preview

Indicates that the track is used in the movie’s preview. Flag value is 0x0004.

Track in poster

Indicates that the track is used in the movie’s poster. Flag value is 0x0008.

Creation time
A 32-bit integer that indicates (in seconds since midnight, January 1, 1904) when the track
header was created.

Modification time
A 32-bit integer that indicates (in seconds since midnight, January 1, 1904) when the track
header was changed.

Track ID
A 32-bit integer that uniquely identifies the track. The value 0 cannot be used.

Reserved
A 32-bit integer that is reserved for use by Apple. Set this field to 0.

Duration
A time value that indicates the duration of this track (in the movie’s time coordinate system).
Note that this property is derived from the track’s edits. The value of this field is equal to the
sum of the durations of all of the track’s edits. If there is no edit list, then the duration is the
sum of the sample durations, converted into the movie timescale.

Reserved
An 8-byte value that is reserved for use by Apple. Set this field to 0.

Layer
A 16-bit integer that indicates this track’s spatial priority in its movie. The QuickTime Movie
Toolbox uses this value to determine how tracks overlay one another. Tracks with lower layer
values are displayed in front of tracks with higher layer values.

Alternate group
A 16-bit integer that specifies a collection of movie tracks that contain alternate data for one
another. QuickTime chooses one track from the group to be used when the movie is played.
The choice may be based on such considerations as playback quality, language, or the
capabilities of the computer.

Volume
A 16-bit fixed-point value that indicates how loudly this track’s sound is to be played. A value
of 1.0 indicates normal volume.

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Reserved
A 16-bit integer that is reserved for use by Apple. Set this field to 0.

Matrix structure
The matrix structure associated with this track. See Figure 4-1 (page 204) for an illustration of
a matrix structure.

Track width
A 32-bit fixed-point number that specifies the width of this track in pixels.

Track height
A 32-bit fixed-point number that indicates the height of this track in pixels.

Clipping Atoms
Clipping atoms specify the clipping regions for movies and for tracks. The clipping atom has an atom
type value of 'clip'.

Figure 2-8 (page 44) shows the layout of a clipping atom.

Figure 2-8 The layout of a clipping atom

Bytes

Clipping atom
Atom size 4

Type = 'clip' 4

Clipping region atom

Atom size 4

Type = 'crgn' 4

Region size 2

Region boundary box 8

Clipping region data Variable

Clipping atoms contain the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this clipping atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'clip'.

Clipping region atom
See “Clipping Region Atoms” (page 45).

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Clipping Region Atoms
The clipping region atom contains the data that specifies the clipping region, including its size,
bounding box, and region. Clipping region atoms have an atom type value of 'crgn'.

The layout of the clipping region atom is shown in Figure 2-8 (page 44).

Clipping region atoms contain the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this clipping region atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'crgn'.

Region size
The region size, region boundary box, and clipping region data fields constitute a QuickDraw
region.

Region boundary box
region.

Clipping region data
region.

Track Matte Atoms
Track matte atoms are used to visually blend the track’s image when it is displayed.

Track matte atoms have an atom type value of 'matt'.

Figure 2-9 (page 46) shows the layout of track matte atoms.

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Figure 2-9 The layout of a track matte atom

Bytes

Track matte atom

Atom size 4

Type = 'matt' 4

Compressed matte atom

Atom size 4

Type = 'kmat' 4

Version 1

Flags 3
Matte image
description structure Variable

Matte data Variable

Track matte atoms contain the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this track matte atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'matt'.

Compressed matte atom

The actual matte data
See “Compressed Matte Atoms” (page 46) for details.

Compressed Matte Atoms
The compressed matte atom specifies the image description structure and the matte data associated
with a particular matte atom. Compressed matte atoms have an atom type value of 'kmat'.

The layout of the compressed matte atom is shown in Figure 2-9 (page 46).

Compressed matte atoms contain the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this compressed matte atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'kmat'.

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Version
A 1-byte specification of the version of this compressed matte atom.

Flags
Three bytes of space for flags. Set this field to 0.

Matte image description structure
An image description structure associated with this matte data. The image description contains
detailed information that governs how the matte data is used. See “Video Sample
Description” (page 94) for more information about image descriptions.

Matte data
The compressed matte data, which is of variable length.

Edit Atoms
You use edit atoms to define the portions of the media that are to be used to build up a track for a
movie. The edits themselves are contained in an edit list table, which consists of time offset and
duration values for each segment. Edit atoms have an atom type value of 'edts'.

Figure 2-10 (page 48) shows the layout of an edit atom.

In the absence of an edit list, the presentation of a track starts immediately. An empty edit is used to
offset the start time of a track.

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Note: If the edit atom or the edit list atom is missing, you can assume that the entire media is used
by the track. <8bat>u

Figure 2-10 The layout of an edit atom

Bytes

Edit atom

Atom size 4

Type = 'edts' 4

Edit list atom

Atom size 4

Type = 'elst' 4

Version 1

Flags 3

Number of entries 4

Edit list table Variable

Edit atoms contain the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this edit atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'edts'.

Edit list atom
See “Edit List Atoms” (page 48).

Edit List Atoms
You use the edit list atom, also shown in Figure 2-10 (page 48), to map from a time in a movie to a
time in a media, and ultimately to media data. This information is in the form of entries in an edit list
table, shown in Figure 2-11 (page 49). Edit list atoms have an atom type value of 'elst'.

Edit list atoms contain the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this edit list atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'elst'.

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Version
A 1-byte specification of the version of this edit list atom.

Flags
Three bytes of space for flags. Set this field to 0.

Number of entries
A 32-bit integer that specifies the number of entries in the edit list atom that follows.

Edit list table
An array of 32-bit values, grouped into entries containing 3 values each. Figure 2-11 (page 49)
shows the layout of the entries in this table.

Figure 2-11 The layout of an edit list table entry

Track duration Media time Media rate Field

4 4 4 Bytes

An edit list table entry contains the following elements.

Track duration
A 32-bit integer that specifies the duration of this edit segment in units of the movie’s time
scale.

Media time
A 32-bit integer containing the starting time within the media of this edit segment (in media
timescale units). If this field is set to –1, it is an empty edit. The last edit in a track should never
be an empty edit. Any difference between the movie’s duration and the track’s duration is
expressed as an implicit empty edit.

Media rate
A 32-bit fixed-point number that specifies the relative rate at which to play the media
corresponding to this edit segment. This rate value cannot be 0 or negative.

Track Load Settings Atoms
Track load settings atoms contain information that indicates how the track is to be used in its movie.
Applications that read QuickTime files can use this information to process the movie data more
efficiently. Track load settings atoms have an atom type value of 'load'.

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Figure 2-12 The layout of a track load settings atom

Bytes
Track load settings atom

Atom size 4

Type = 'load' 4

Preload start time 4

Preload duration 4

Preload flags 4

Default hints 4

Track load settings atoms contain the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this track load settings atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'load'.

Preload start time
A 32-bit integer specifying the starting time, in the movie’s time coordinate system, of a segment
of the track that is to be preloaded. Used in conjunction with the preload duration.

Preload duration
A 32-bit integer specifying the duration, in the movie’s time coordinate system, of a segment
of the track that is to be preloaded. If the duration is set to –1, it means that the preload segment
extends from the preload start time to the end of the track. All media data in the segment of
the track defined by the preload start time and preload duration values should be loaded into
memory when the movie is to be played.

Preload flags
A 32-bit integer containing flags governing the preload operation. Only two flags are defined,
and they are mutually exclusive. If preload flags is set to 1, the track is to be preloaded regardless
of whether it is enabled. If preload flags is set to 2, the track is to be preloaded only if it is
enabled.

Default hints
A 32-bit integer containing playback hints. More than one flag may be enabled. Flags are
enabled by setting them to 1. The following flags are defined.
Double buffer

This flag indicates that the track should be played using double-buffered I/O. This flag’s value
is 0x0020.

High quality

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This flag indicates that the track should be displayed at highest possible quality, without regard
to real-time performance considerations. This flag’s value is 0x0100.

Track Reference Atoms
Track reference atoms define relationships between tracks. Track reference atoms allow one track to
specify how it is related to other tracks. For example, if a movie has three video tracks and three sound
tracks, track references allow you to identify the related sound and video tracks. Track reference
atoms have an atom type value of 'tref'.

Track references are uni-directional and point from the recipient track to the source track. For example,
a video track may reference a time code track to indicate where its time code is stored, but the time
code track would not reference the video track. The time code track is the source of time information
for the video track.

A single track may reference multiple tracks. For example, a video track could reference a sound track
to indicate that the two are synchronized and a time code track to indicate where its time code is
stored.

A single track may also be referenced by multiple tracks. For example, both a sound and video track
could reference the same time code track if they share the same timing information.

If this atom is not present, the track is not referencing any other track in any way. Note that the array
of track reference type atoms is sized to fill the track reference atom. Track references with a reference
index of 0 are permitted. This indicates no reference.

Figure 2-13 (page 51) shows the layout of a track reference atom.

Figure 2-13 The layout of a track reference atom

Track reference atom Bytes

Atom size 4

Type = 'tref' 4

Track reference type atom

Atom size 4

Type = (see table) 4

Track IDs Variable

A track reference atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this track reference atom.

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Type
A 32-bit integer that identifies the atom type; this field must be set to 'tref'.

Track reference type atoms
A list of track reference type atoms containing the track reference information. These atoms
are described next.

Each track reference atom defines relationships with tracks of a specific type. The reference type
implies a track type. Table 2-2 (page 52) shows the track reference types and their descriptions.

Table 2-2 Track reference types

Reference
Description
type

'tmcd' Time code. Usually references a time code track.

'chap' Chapter or scene list. Usually references a text track.

'sync' Synchronization. Usually between a video and sound track. Indicates
that the two tracks are synchronized. The reference can be from either
track to the other, or there may be two references.

'scpt' Transcript. Usually references a text track.

'ssrc' Nonprimary source. Indicates that the referenced track should send
its data to this track, rather than presenting it. The referencing track
will use the data to modify how it presents its data. See “Track Input
Map Atoms” (page 53) for more information.

'hint' The referenced tracks contain the original media for this hint track.

Each track reference type atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this track reference type atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to one of the values shown
in Table 2-2 (page 52).

Track IDs
A list of track ID values (32-bit integers) specifying the related tracks. Note that this is one case
where track ID values can be set to 0. Unused entries in the atom may have a track ID value
of 0. Setting the track ID to 0 may be more convenient than deleting the reference.

You can determine the number of track references stored in a track reference type atom by subtracting
its header size from its overall size and then dividing by the size, in bytes, of a track ID.

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Track Input Map Atoms
Track input map atoms define how data being sent to this track from its nonprimary sources is to be
interpreted. Track references of type 'ssrc' define a track’s secondary data sources. These sources
provide additional data that is to be used when processing the track. Track input map atoms have
an atom type value of 'imap'.

Figure 2-14 (page 53) shows the layout of a track input atom. This atom contains one or more track
input atoms. Note that the track input map atom is a QT atom structure.

Figure 2-14 The layout of a track input map atom

Track input map atom Bytes

Atom size 4

Type = 'imap' 4

Track input atom

Atom size 4

Type = ' in' 4

Atom ID 4

Reserved 2

Child count 2

Reserved 4

Input type atom ‡

Atom size 4

Type = ' ty' 4

Input type 4

Object ID atom

Atom size 4

Type = 'obid' 4

Object ID 4

‡ Required atom

Each track input map atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this track input map atom.

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Type
A 32-bit integer that identifies the atom type; this field must be set to 'imap'.

Track input atoms
A list of track input atoms specifying how to use the input data.

The input map defines all of the track’s secondary inputs. Each secondary input is defined using a
separate track input atom.

Each track input atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this track input atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to ' in' (note that the two
leading bytes must be set to 0x00).

Atom ID
A 32-bit integer relating this track input atom to its secondary input. The value of this field
corresponds to the index of the secondary input in the track reference atom. That is, the first
secondary input corresponds to the track input atom with an atom ID value of 1; the second
to the track input atom with an atom ID of 2, and so on.

Reserved

Child count
A 16-bit integer specifying the number of child atoms in this atom.

Reserved

The track input atom, in turn, may contain two other types of atoms: input type atoms and object ID
atoms. The input type atom is required; it specifies how the data is to be interpreted.

The input type atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this input type atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to ' ty' (note that the two
leading bytes must be set to 0x00).

Input type
A 32-bit integer that specifies the type of data that is to be received from the secondary data
source. Table 2-3 (page 55) lists valid values for this field.

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Table 2-3 Input types

Input identifier Value Description

kTrackModifierTypeMatrix 1 A 3x3 transformation matrix to transform the
track’s location, scaling, and so on.

kTrackModifierTypeClip 2 A QuickDraw clipping region to change the track’s
shape.

kTrackModifierTypeVolume 3 An 8.8 fixed-point value indicating the relative
sound volume. This is used for fading the volume.

kTrackModifierTypeBalance 4 A 16-bit integer indicating the sound balance level.
This is used for panning the sound location.

kTrackModifierTypeGraphicsMode 5 A graphics mode record (32-bit integer indicating
graphics mode, followed by an RGB color) to
modify the track’s graphics mode for visual fades.

kTrackModifierObjectMatrix 6 A 3x3 transformation matrix to transform an object
within the track’s location, scaling, and so on.

kTrackModifierObjectGraphicsMode 7 A graphics mode record (32-bit integer indicating
graphics mode, followed by an RGB color) to
modify an object within the track’s graphics mode
for visual fades.

kTrackModifierTypeImage 'vide’ Compressed image data for an object within the
track. Note that this was
kTrackModifierTypeSpriteImage.

If the input is operating on an object within the track (for example, a sprite within a sprite track), an
object ID atom must be included in the track input atom to identify the object.

The object ID atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this object ID atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'obid'.

Object ID
A 32-bit integer identifying the object.

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Media Atoms

Media atoms describe and define a track’s media type and sample data. The media atom contains
information that specifies the media type, such as sound or video, the media handler component used
to interpret the sample data, the media timescale and track duration, and media-and-track-specific
information such as sound volume or graphics mode. It also contains the media data references, which
typically specify the file where the sample data is stored, and the sample table atoms, which specify
the sample description, duration, and byte offset from the data reference for each media sample.

The media atom has an atom type of 'mdia'. It must contain a media header atom ('mdhd'), and it
can contain a handler reference ('hdlr'), media information ('minf'), and user data ('udta').

Figure 2-15 (page 56) shows the layout of a media atom.

Figure 2-15 The layout of a media atom

Media atom
Atom size
Type = 'mdia'

Media header atom 'mdhd' ‡

Handler reference atom 'hdlr'

Media information atom 'minf'


‡ Required atom

Media atoms contain the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this media atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'mdia'.

Media header atom
This atom contains the standard media information. See “Media Header Atoms” (page 57).

Handler reference atom
This atom identifies the media handler component that is to be used to interpret the media
data. See “Handler Reference Atoms” (page 58) for more information.

Note that the handler reference atom tells you the kind of media this media atom contains—for
example, video or sound. The layout of the media information atom is specific to the media
handler that is to interpret the media. “Media Information Atoms” (page 60) discusses how
data may be stored in a media, using the video media format defined by Apple as an example.

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Media information atom
This atom contains data specific to the media type for use by the media handler component.
See “Media Information Atoms” (page 60).

User data atom
See “User Data Atoms” (page 36).

Media Header Atoms
The media header atom specifies the characteristics of a media, including time scale and duration.
The media header atom has an atom type of 'mdhd'.

Figure 2-16 (page 57) shows the layout of the media header atom.

Figure 2-16 The layout of a media header atom

Bytes

Media header atom

Atom size 4

Type = 'mdhd' 4

Version 1

Flags 3

Creation time 4

Modification time 4

Time scale 4

Duration 4

Language 2

Quality 2

Media header atoms contain the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this media header atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'mdhd'.

Version
One byte that specifies the version of this header atom.

Flags
Three bytes of space for media header flags. Set this field to 0.

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Creation time
A 32-bit integer that specifies (in seconds since midnight, January 1, 1904) when the media
atom was created.

Modification time
A 32-bit integer that specifies (in seconds since midnight, January 1, 1904) when the media
atom was changed.

Time scale
A time value that indicates the time scale for this media—that is, the number of time units that
pass per second in its time coordinate system.

Duration
The duration of this media in units of its time scale.

Language
A 16-bit integer that specifies the language code for this media. See “Language Code
Values” (page 201) for valid language codes.

Quality
A 16-bit integer that specifies the media’s playback quality—that is, its suitability for playback
in a given environment.

Handler Reference Atoms
The handler reference atom specifies the media handler component that is to be used to interpret the
media’s data. The handler reference atom has an atom type value of 'hdlr'.

Historically, the handler reference atom was also used for data references. However, this use may
now be ignored.

The handler atom within a media atom declares the process by which the media data in the stream
may be presented, and thus, the nature of the media in a stream. For example, a video handler would
handle a video track.

Figure 2-17 (page 59) shows the layout of a handler reference atom.

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Figure 2-17 The layout of a handler reference atom

Bytes

Atom size 4

Type = 'hdlr' 4

Version 1

Flags 3

Component type 4

Component subtype 4

Component manufacturer 4

Component flags 4

Component flags mask 4

Component name Variable

Handler reference atoms contain the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this handler reference atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'hdlr'.

Version
A 1-byte specification of the version of this handler information.

Flags
A 3-byte space for handler information flags. Set this field to 0.

Component type
A four-character code that identifies the type of the handler. Only two values are valid for this
field: 'mhlr' for media handlers and 'dhlr' for data handlers.

Component subtype
A four-character code that identifies the type of the media handler or data handler. For media
handlers, this field defines the type of data—for example, 'vide' for video data or 'soun' for
sound data.

For data handlers, this field defines the data reference type—for example, a component subtype
value of 'alis' identifies a file alias.

Component manufacturer
Reserved. Set to 0.

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Component flags
Reserved. Set to 0.

Component flags mask
Reserved. Set to 0.

Component name
A (counted) string that specifies the name of the component—that is, the media handler used
when this media was created. This field may contain a zero-length (empty) string.

Media Information Atoms
Media information atoms (defined by the 'minf' atom type) store handler-specific information for
a track’s media data. The media handler uses this information to map from media time to media data
and to process the media data.

These atoms contain information that is specific to the type of data defined by the media. Further,
the format and content of media information atoms are dictated by the media handler that is responsible
for interpreting the media data stream. Another media handler would not know how to interpret this
information.

This section describes the atoms that store media information for the video ('vmhd'), sound ('smhd'),
and base ('gmhd') portions of QuickTime movies.

Note: “Using Sample Atoms” (page 82) discusses how the video media handler locates samples in
a video media. <8bat>u

Video Media Information Atoms
Video media information atoms are the highest-level atoms in video media. These atoms contain a
number of other atoms that define specific characteristics of the video media data. Figure 2-18 (page 60)
shows the layout of a video media information atom.

Figure 2-18 The layout of a media information atom for video


Atom size
Type = 'minf'

Video media information header atom 'vmhd' ‡

Handler reference atom 'hdlr' ‡

Data information atom 'dinf'

Sample table atom 'stbl'

‡ Required atom

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The video media information atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this video media information atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'minf'.

See “Video Media Information Header Atoms” (page 61).

See “Handler Reference Atoms” (page 58).

See “Data Information Atoms” (page 66).

Sample table atom
See “Sample Table Atoms” (page 70).

Video Media Information Header Atoms
Video media information header atoms define specific color and graphics mode information.

Figure 2-19 (page 61) shows the structure of a video media information header atom.

Figure 2-19 The layout of a media information header atom for video

Bytes

Video media information header atom

Atom size 4

Type = 'vmhd' 4

Version 1

Flags 3

Graphics mode 2

Opcolor 6

The video media information header atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this video media information header
atom.

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Type
A 32-bit integer that identifies the atom type; this field must be set to 'vmhd'.

Version
A 1-byte specification of the version of this video media information header atom.

Flags
A 3-byte space for video media information flags. There is one defined flag.
No lean ahead

This is a compatibility flag that allows QuickTime to distinguish between movies created with
QuickTime 1.0 and newer movies. You should always set this flag to 1, unless you are creating
a movie intended for playback using version 1.0 of QuickTime. This flag’s value is 0x0001.

Graphics mode
A 16-bit integer that specifies the transfer mode. The transfer mode specifies which Boolean
operation QuickDraw should perform when drawing or transferring an image from one location
to another. See “Graphics Modes” (page 204) for a list of graphics modes supported by
QuickTime.

Opcolor
Three 16-bit values that specify the red, green, and blue colors for the transfer mode operation
indicated in the graphics mode field.

Sound Media Information Atoms
Sound media information atoms are the highest-level atoms in sound media. These atoms contain a
number of other atoms that define specific characteristics of the sound media data. Figure
2-20 (page 62) shows the layout of a sound media information atom.

Figure 2-20 The layout of a media information atom for sound

Sound media information atom

Atom size
Type = 'minf'

Sound media information header atom 'smhd' ‡

Handler reference atom 'hdlr' ‡

Data information atom 'dinf'

Sample table atom 'stbl'

‡ Required atom

The sound media information atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this sound media information atom.

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Type

Sound media information header atom
See “Sound Media Information Header Atoms” (page 63).

See “Handler Reference Atoms” (page 58).

See “Data Information Atoms” (page 66).

Sample table atom
See “Sample Table Atoms” (page 70).

Sound Media Information Header Atoms
The sound media information header atom (shown in Figure 2-21 (page 63)) stores the sound media’s
control information, such as balance.

Figure 2-21 The layout of a sound media information header atom

Bytes
Sound media information
header atom
Atom size 4

Type = 'smhd' 4

Version 1

Flags 3

Balance 2

Reserved 2

The sound media information header atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this sound media information header
atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'smhd'.

Version
A 1-byte specification of the version of this sound media information header atom.

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Flags
A 3-byte space for sound media information flags. Set this field to 0.

Balance
A 16-bit integer that specifies the sound balance of this sound media. Sound balance is the
setting that controls the mix of sound between the two speakers of a computer. This field is
normally set to 0. See “Balance” (page 206) for more information about balance values.

Reserved
Reserved for use by Apple. Set this field to 0.

Base Media Information Atoms
The base media information atom (shown in Figure 2-22 (page 64)) stores the media information for
media types such as text, MPEG, time code, and music.

Media types that are derived from the base media handler may add other atoms within the base
media information atom, as appropriate. At present, the only media type that defines any additional
atoms is the timecode media. See “Timecode Media Information Atom” (page 109) for more information
about timecode media.

Figure 2-22 The layout of a base media information atom

Base media information atom

Atom size
Type = 'minf'

Base media information header atom 'gmhd' ‡

Base media info atom 'gmin' ‡

‡ Required atom

The base media information atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this base media information atom.

Type

Base media information header atom
See “Base Media Information Header Atoms” (page 65).

Base media info atom
See “Base Media Info Atoms” (page 65).

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Base Media Information Header Atoms
The base media information header atom indicates that this media information atom pertains to a
base media.

The base media information header atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this base media information header atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'gmhd'.

Base Media Info Atoms
The base media info atom, contained in the base media information atom, defines the media’s control
information, including graphics mode and balance information.

Figure 2-23 (page 65) shows the layout of the base media info atom.

Figure 2-23 The layout of a base media info atom

Base media info atom Bytes

Atom size 4

Type = 'gmin' 4

Version 1

Flags 3

Graphics mode 2

Opcolor 6

Balance 2

Reserved 2

The base media info atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this base media info atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'gmin'.

Version
A 1-byte specification of the version of this base media information header atom.

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Flags
A 3-byte space for base media information flags. Set this field to 0.

Graphics mode
A 16-bit integer that specifies the transfer mode. The transfer mode specifies which Boolean
operation QuickDraw should perform when drawing or transferring an image from one location
to another. See “Graphics Modes” (page 204) for more information about graphics modes
supported by QuickTime.

Opcolor
Three 16-bit values that specify the red, green, and blue colors for the transfer mode operation
indicated in the graphics mode field.

Balance
A 16-bit integer that specifies the sound balance of this media. Sound balance is the setting
that controls the mix of sound between the two speakers of a computer. This field is normally
set to 0. See “Balance” (page 206) for more information about balance values.

Reserved
Reserved for use by Apple. Set this field to 0.

Data Information Atoms
The handler reference atom (described in “Handler Reference Atoms” (page 58)) contains information
specifying the data handler component that provides access to the media data. The data handler
component uses the data information atom to interpret the media’s data. Data information atoms
have an atom type value of 'dinf'.

Figure 2-24 (page 67) shows the layout of the data information atom.

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Figure 2-24 The layout of a data information atom

Bytes


Atom size 4

Type = 'dinf' 4

Data reference atom

Atom size 4

Type = 'dref' 4

Version 1

Flags 3

Number of entries 4

Data references

Size 4

Type 4

Version 1

Flags 3

Data Variable
.
.
.
Size 4

Type 4

Version 1

Flags 3

Data Variable

The data information atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this data information atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'dinf'.

Data reference atom
See “Data Reference Atoms” (page 68).

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Data Reference Atoms
Data reference atoms contain tabular data that instructs the data handler component how to access
the media’s data. Figure 2-24 (page 67) shows the data reference atom.

The data reference atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this data reference atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'dref'.

Version
A 1-byte specification of the version of this data reference atom.

Flags
A 3-byte space for data reference flags. Set this field to 0.

Number of entries
A 32-bit integer containing the count of data references that follow.

Data references
An array of data references.

Each data reference is formatted like an atom and contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in the data reference.

Type
A 32-bit integer that specifies the type of the data in the data reference. Table 2-4 (page 69)
lists valid type values.

Version
A 1-byte specification of the version of the data reference.

Flags
A 3-byte space for data reference flags. There is one defined flag.
Self reference

This flag indicates that the media’s data is in the same file as the movie atom. On the Macintosh,
and other file systems with multifork files, set this flag to 1 even if the data resides in a different
fork from the movie atom. This flag’s value is 0x0001.

Data
The data reference information.

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Table 2-4 (page 69) shows the currently defined data reference types that may be stored in a header
atom.

Table 2-4 Data reference types

Data reference
Description
type

'alis' Data reference is a Macintosh alias. An alias contains information
about the file, including its full path name.

'rsrc' Data reference is a Macintosh alias. Appended to the end of the
alias is the resource type (stored as a 32-bit integer) and ID (stored
as a 16-bit signed integer) to use within the specified file.

'url ' A C string that specifies a URL. There may be additional data
after the C string.

Sample Atoms

QuickTime stores media data in samples. A sample is a single element in a sequence of time-ordered
data. Samples are stored in the media, and they may have varying durations.

Samples are stored in a series of chunks in a media. Chunks are a collection of data samples in a media
that allow optimized data access. A chunk may contain one or more samples. Chunks in a media may
have different sizes, and the individual samples within a chunk may have different sizes from one
another, as shown in Figure 2-25 (page 70).

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Figure 2-25 Samples in a media

Data stream

Sample 1

Chunk 1 Sample 2

Sample 3

Sample 4

Chunk 2
Sample 5

Sample 6

Chunk 3
Sample 7

Chunk 4 Sample 8

Chunk 5 Sample 9

One way to describe a sample is to use a sample table atom. The sample table atom acts as a storehouse
of information about the samples and contains a number of different types of atoms. The various
atoms contain information that allows the media handler to parse the samples in the proper order.
This approach enforces an ordering of the samples without requiring that the sample data be stored
sequentially with respect to movie time in the actual data stream.

The next section discusses the sample table atom. Subsequent sections discuss each of the atoms that
may reside in a sample table atom.

Sample Table Atoms
The sample table atom contains information for converting from media time to sample number to
sample location. This atom also indicates how to interpret the sample (for example, whether to
decompress the video data and, if so, how). This section describes the format and content of the sample
table atom.

The sample table atom has an atom type of 'stbl'. It can contain the sample description atom, the
time-to-sample atom, the sync sample atom, the sample-to-chunk atom, the sample size atom, the
chunk offset atom, and the shadow sync atom.

The sample table atom contains all the time and data indexing of the media samples in a track. Using
tables, it is possible to locate samples in time, determine their type, and determine their size, container,
and offset into that container.

If the track that contains the sample table atom references no data, then the sample table atom does
not need to contain any child atoms (not a very useful media track).

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If the track that the sample table atom is contained in does reference data, then the following child
atoms are required: sample description, sample size, sample to chunk, and chunk offset. All of the
subtables of the sample table use the same total sample count.

The sample description atom must contain at least one entry. A sample description atom is required
because it contains the data reference index field that indicates which data reference atom to use to
retrieve the media samples. Without the sample description, it is not possible to determine where the
media samples are stored. The sync sample atom is optional. If the sync sample atom is not present,
all samples are implicitly sync samples.

Figure 2-26 (page 71) shows the layout of the sample table atom.

Figure 2-26 The layout of a sample table atom

Sample table atom
Atom size
Type ='stbl'

Sample description atom 'stsd'

Time-to-sample atom 'stts'

Sync sample atom 'stss'

Sample-to-chunk atom 'stsc'

Sample size atom 'stsz'
Chunk offset atom 'stco'

Shadow sync atom 'stsh'

The sample table atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this sample table atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'stbl'.

Sample description atom
See “Sample Description Atoms” (page 72).

Time-to-sample atom
See “Time-to-Sample Atoms” (page 73).

Sync sample atom
See “Sync Sample Atoms” (page 75).

Sample-to-chunk atom
See “Sample-to-Chunk Atoms” (page 77).

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Sample size atom
See “Sample Size Atoms” (page 79).

Chunk offset atom
See “Chunk Offset Atoms” (page 80).

Shadow sync atom
Reserved for future use.

Sample Description Atoms
The sample description atom stores information that allows you to decode samples in the media. The
data stored in the sample description varies, depending on the media type. For example, in the case
of video media, the sample descriptions are image description structures. The sample description
information for each media type is explained in Chapter 4, “Media Data Atom Types.” (page 93)

Figure 2-27 (page 72) shows the layout of the sample description atom.

Figure 2-27 The layout of a sample description atom

Bytes
Sample description atom

Atom size 4

Type = 'stsd' 4

Version 1

Flags 3

Number of entries 4

Sample description table Variable

The sample description atom has an atom type of 'stsd'. The sample description atom contains a
table of sample descriptions. A media may have one or more sample descriptions, depending upon
the number of different encoding schemes used in the media and on the number of files used to store
the data. The sample-to-chunk atom identifies the sample description for each sample in the media
by specifying the index into this table for the appropriate description (see “Sample-to-Chunk
Atoms” (page 77)).

The sample description atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this sample description atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'stsd'.

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Version
A 1-byte specification of the version of this sample description atom.

Flags
A 3-byte space for sample description flags. Set this field to 0.

Number of entries
A 32-bit integer containing the number of sample descriptions that follow.

Sample description table
An array of sample descriptions.

Sample description table

While the exact format of the sample description varies by media type, the first four fields of every
sample description are the same. See Chapter 4, “Media Data Atom Types,” (page 93) for details on
various media.

Sample description size
A 32-bit integer indicating the number of bytes in the sample description.

Data format
A 32-bit integer indicating the format of the stored data. This depends on the media type, but
is usually either the compression format or the media type.

Reserved
Six bytes that must be set to 0.

Data reference index
A 16-bit integer that contains the index of the data reference to use to retrieve data associated
with samples that use this sample description. Data references are stored in data reference
atoms.

Time-to-Sample Atoms
Time-to-sample atoms store duration information for a media’s samples, providing a mapping from
a time in a media to the corresponding data sample. The time-to-sample atom has an atom type of
'stts'.

You can determine the appropriate sample for any time in a media by examining the time-to-sample
atom table, which is contained in the time-to-sample atom.

The atom contains a compact version of a table that allows indexing from time to sample number.
Other tables provide sample sizes and pointers from the sample number. Each entry in the table gives
the number of consecutive samples with the same time delta, and the delta of those samples. By
adding the deltas, a complete time-to-sample map can be built.

The atom contains time deltas: DT(n+1) = DT(n) + STTS(n) where STTS(n) is the (uncompressed)
table entry for sample n and DT is the display time for sample (n). The sample entries are ordered by
time stamps; therefore, the deltas are all nonnegative. The DT axis has a zero origin; DT(i) = SUM

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(for j=0 to i-1 of delta(j)), and the sum of all deltas gives the length of the media in the track
(not mapped to the overall time scale, and not considering any edit list). The edit list atom provides
the initial DT value if it is nonempty (nonzero).

Figure 2-28 (page 74) shows the layout of the time-to-sample atom.

Figure 2-28 The layout of a time-to-sample atom

Bytes
Time-to-sample atom

Atom size 4

Type = 'stts' 4

Version 1

Flags 3

Number of entries 4

Time-to-sample table Variable

The time-to-sample atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this time-to-sample atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'stts'.

Version
A 1-byte specification of the version of this time-to-sample atom.

Flags
A 3-byte space for time-to-sample flags. Set this field to 0.

Number of entries
A 32-bit integer containing the count of entries in the time-to-sample table.

Time-to-sample table
A table that defines the duration of each sample in the media. Each table entry contains a count
field and a duration field. The structure of the time-to-sample table is shown in Figure
2-29 (page 74).

Figure 2-29 The layout of a time-to-sample table entry

Sample count Sample duration Field

4 4 Bytes

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You define a time-to-sample table entry by specifying these fields:

Sample count
A 32-bit integer that specifies the number of consecutive samples that have the same duration.

Sample duration
A 32-bit integer that specifies the duration of each sample.

Sample duration

Entries in the table describe samples according to their order in the media and their duration. If
consecutive samples have the same duration, a single table entry can be used to define more than one
sample. In these cases, the count field indicates the number of consecutive samples that have the same
duration. For example, if a video media has a constant frame rate, this table would have one entry
and the count would be equal to the number of samples.

Figure 2-30 (page 75) presents an example of a time-to-sample table that is based on the chunked
media data shown in Figure 3-25 (page 70). That data stream contains a total of nine samples that
correspond in count and duration to the entries of the table shown here. Even though samples 4, 5,
and 6 are in the same chunk, sample 4 has a duration of 3, and samples 5 and 6 have a duration of 2.

Figure 2-30 An example of a time-to-sample table

Sample Sample
count duration

4 3

2 1

3 2

Sync Sample Atoms
The sync sample atom identifies the key frames in the media. In a media that contains compressed
data, key frames define starting points for portions of a temporally compressed sequence. The key
frame is self-contained—that is, it is independent of preceding frames. Subsequent frames may depend
on the key frame.

The sync sample atom provides a compact marking of the random access points within a stream. The
table is arranged in strictly increasing order of sample number. If this table is not present, every
sample is implicitly a random access point.

Sync sample atoms have an atom type of 'stss'. The sync sample atom contains a table of sample
numbers. Each entry in the table identifies a sample that is a key frame for the media. If no sync
sample atom exists, then all the samples are key frames.

Figure 2-31 (page 76) shows the layout of a sync sample atom.

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Figure 2-31 The layout of a sync sample atom

Bytes
Sync sample atom

Atom size 4

Type = 'stss' 4

Version 1

Flags 3

Number of entries 4

Sync sample table Variable

The sync sample atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this sync sample atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'stss'.

Version
A 1-byte specification of the version of this sync sample atom.

Flags
A 3-byte space for sync sample flags. Set this field to 0.

Number of entries
A 32-bit integer containing the count of entries in the sync sample table.

Sync sample table
A table of sample numbers; each sample number corresponds to a key frame. Figure
2-32 (page 76) shows the layout of the sync sample table.

Figure 2-32 The layout of a sync sample table

Number Sample 1

Number Sample 2

Number Sample 3

Number Sample 4
Number Sample 5

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Sample-to-Chunk Atoms
As samples are added to a media, they are collected into chunks that allow optimized data access. A
chunk contains one or more samples. Chunks in a media may have different sizes, and the samples
within a chunk may have different sizes. The sample-to-chunk atom stores chunk information for the
samples in a media.

Sample-to-chunk atoms have an atom type of 'stsc'. The sample-to-chunk atom contains a table
that maps samples to chunks in the media data stream. By examining the sample-to-chunk atom, you
can determine the chunk that contains a specific sample.

Figure 2-33 (page 77) shows the layout of the sample-to-chunk atom.

Figure 2-33 The layout of a sample-to-chunk atom

Bytes
Sample-to-chunk atom

Atom size 4

Type = 'stsc' 4

Version 1

Flags 3

Number of entries 4

Sample-to-chunk table Variable

The sample-to-chunk atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this sample-to-chunk atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'stsc'.

Version
A 1-byte specification of the version of this sample-to-chunk atom.

Flags
A 3-byte space for sample-to-chunk flags. Set this field to 0.

Number of entries
A 32-bit integer containing the count of entries in the sample-to-chunk table.

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Sample-to-chunk table
A table that maps samples to chunks. Figure 2-34 (page 78) shows the structure of an entry in
a sample-to-chunk table. Each sample-to-chunk atom contains such a table, which identifies
the chunk for each sample in a media. Each entry in the table contains a first chunk field, a
samples per chunk field, and a sample description ID field. From this information, you can
ascertain where samples reside in the media data.

Figure 2-34 The layout of a sample-to-chunk table entry

First chunk Samples per chunk Sample description ID Fields

4 4 4 Bytes

You define a sample-to-chunk table entry by specifying the following data elements.

First chunk
The first chunk number using this table entry.

Samples per chunk
The number of samples in each chunk.

Sample description ID
The identification number associated with the sample description for the sample. For details
on sample description atoms, see “Sample Description Atoms” (page 72).

Figure 2-35 (page 78) shows an example of a sample-to-chunk table that is based on the data stream
shown in Figure 3-25 (page 70).

Figure 2-35 An example of a sample-to-chunk table

First Samples Sample
chunk per chunk description ID

1 3 23

3 1 23

5 1 24

Each table entry corresponds to a set of consecutive chunks, each of which contains the same number
of samples. Furthermore, each of the samples in these chunks must use the same sample description.
Whenever the number of samples per chunk or the sample description changes, you must create a
new table entry. If all the chunks have the same number of samples per chunk and use the same
sample description, this table has one entry.

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Sample Size Atoms
You use sample size atoms to specify the size of each sample in the media. Sample size atoms have
an atom type of 'stsz'.

The sample size atom contains the sample count and a table giving the size of each sample. This allows
the media data itself to be unframed. The total number of samples in the media is always indicated
in the sample count. If the default size is indicated, then no table follows.

Figure 2-36 (page 79) shows the layout of the sample size atom.

Figure 2-36 The layout of a sample size atom

Bytes
Sample size atom

Atom size 4

Type = 'stsz' 4

Version 1

Flags 3

Sample size 4

Number of entries 4

Sample size table Variable

The sample size atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this sample size atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'stsz'.

Version
A 1-byte specification of the version of this sample size atom.

Flags
A 3-byte space for sample size flags. Set this field to 0.

Sample size
A 32-bit integer specifying the sample size. If all the samples are the same size, this field contains
that size value. If this field is set to 0, then the samples have different sizes, and those sizes are
stored in the sample size table.

Number of entries
A 32-bit integer containing the count of entries in the sample size table.

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Sample size table
A table containing the sample size information. The sample size table contains an entry for
every sample in the media’s data stream. Each table entry contains a size field. The size field
contains the size, in bytes, of the sample in question. The table is indexed by sample
number—the first entry corresponds to the first sample, the second entry is for the second
sample, and so on.

Figure 2-37 (page 80) shows a sample size table.

Figure 2-37 An example of a sample size table

Size Sample 1

Size Sample 2

Size Sample 3

Size Sample 4

Size Sample 5

Chunk Offset Atoms
Chunk offset atoms identify the location of each chunk of data in the media’s data stream. Chunk
offset atoms have an atom type of 'stco'.

The chunk-offset table gives the index of each chunk into the containing file. There are two variants,
permitting the use of 32-bit or 64-bit offsets. The latter is useful when managing very large movies.
Only one of these variants occurs in any single instance of a sample table atom.

Note that offsets are file offsets, not the offset into any atom within the file (for example, a 'mdat'
atom). This permits referring to media data in files without any atom structure. However, be careful
when constructing a self-contained QuickTime file with its meta-data (movie atom) at the front because
the size of the movie atom affects the chunk offsets to the media data.

Note: The sample table atom can contain a 64-bit chunk offset atom (STChunkOffset64AID = 'co64').
When this atom appears, it is used in place of the original chunk offset atom, which can contain only
32-bit offsets. When QuickTime writes movie files, it uses the 64-bit chunk offset atom only if there
are chunks that use the high 32-bits of the chunk offset. Otherwise, the original 32-bit chunk offset
atom is used to ensure compatibility with previous versions of QuickTime. u

Figure 2-38 (page 81) shows the layout of a chunk offset atom.

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Figure 2-38 The layout of a chunk offset atom

Bytes
Chunk offset atom

Atom size 4

Type = 'stco' 4

Version 1

Flags 3

Number of entries 4

Chunk offset table Variable

The chunk offset atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this chunk offset atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'stco'.

Version
A 1-byte specification of the version of this chunk offset atom.

Flags
A 3-byte space for chunk offset flags. Set this field to 0.

Number of entries
A 32-bit integer containing the count of entries in the chunk offset table.

Chunk offset table
A chunk offset table consisting of an array of offset values. There is one table entry for each
chunk in the media. The offset contains the byte offset from the beginning of the data stream
to the chunk. The table is indexed by chunk number—the first table entry corresponds to the
first chunk, the second table entry is for the second chunk, and so on.

Figure 2-39 (page 82) shows an example of a chunk offset table.

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Figure 2-39 An example of a chunk offset table

Offset Chunk 1

Offset Chunk 2

Offset Chunk 3

Offset Chunk 4
Offset Chunk 5

Using Sample Atoms
This section presents examples using the atoms just described. These examples are intended to help
you understand the relationships between these atoms.

The first section, “Finding a Sample” (page 82), describes the steps that the video media handler uses
to find the sample that contains the media data for a particular time in a media. The second section,
“Finding a Key Frame” (page 82), describes the steps that the video media handler uses to find an
appropriate key frame for a specific time in a movie.

Finding a Sample

When QuickTime displays a movie or track, it “tells” the appropriate media handler to access the
media data for a particular time. The media handler must correctly interpret the data stream to retrieve
the requested data. In the case of video media, the media handler traverses several atoms to find the
location and size of a sample for a given media time.

The media handler performs the following steps:

1. Determines the time in the media time coordinate system.

2. Examines the time-to-sample atom to determine the sample number that contains the data for
the specified time.

3. Scans the sample-to-chunk atom to discover which chunk contains the sample in question.

4. Extracts the offset to the chunk from the chunk offset atom.

5. Finds the offset within the chunk and the sample’s size by using the sample size atom.

Finding a Key Frame

Finding a key frame for a specified time in a movie is slightly more complicated than finding a sample
for a specified time. The media handler must use the sync sample atom and the time-to-sample atom
together in order to find a key frame.

The media handler performs the following steps:

1. Examines the time-to-sample atom to determine the sample number that contains the data for
the specified time.

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2. Scans the sync sample atom to find the key frame that precedes the sample number chosen in
step 1.

3. Scans the sample-to-chunk atom to discover which chunk contains the key frame.

4. Extracts the offset to the chunk from the chunk offset atom.

5. Finds the offset within the chunk and the sample’s size by using the sample size atom.

Compressed Movie Resources

Most QuickTime movies have meta-data in addition to their media data. Media data can be compressed
using a variety of video and sound compression algorithms. Beginning with QuickTime 3, it also
became possible to compress the meta-data––more commonly known as the movie resource. However,
the movie resource cannot be compressed by means of a lossy compression algorithm because it
contains critical information, such as the video and audio compression types used, individual frame
offsets, and timing information. To compress the movie resource, therefore, lossless data compression
algorthms must be used.

Compressing movie resources using data compression typically reduces the size of the movie resource
by 50% or more. For QuickTime movies that are streamed over the Internet, this can substantially
reduce the startup latency of the movie, and therefore has a number of distinct advantages.

Allowing QuickTime to Compress the Movie Resource
Most application developers won’t need to know the details of how movie resources are compressed.
The Movie Toolbox FlattenMovie and FlattenMovieData functions compress the movie resource
if so requested by the application. To accomplish this, applications only need to set the
flattenCompressMovieResource flag when calling either function. The QuickTime movie export
component also provides users with the option of compressing the movie resource when exporting
or creating a new movie through export.

Structure of a Compressed Movie Resource
A compressed movie resource, similar to an uncompressed movie resource, is made up of a group
of QuickTime atoms arranged in a hierarchy.

Like an uncompressed movie resource, the outermost atom is a movie atom. Within the movie atom,
there is a single compressed movie atom, which contains all other required atoms. The compressed
movie atom has two subatoms. The first is a data compression atom, which contains a single 32-bit
integer that identifies what lossless data compression algorithm was used to compress the movie
resource. The second child atom is the compressed movie data, which contains the compressed movie
resource itself. The first 32-bit integer in the compressed movie data atom indicates the uncompressed
size of the movie resource, and then the compressed movie resource data follows.

The contents of a complete compressed movie are shown in Table 2-5 (page 84). The constants that
define the atom types are defined in MoviesFormat.h. The four-character codes for each atom type
are also shown.

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Movie Atoms

Table 2-5 Contents of complete compressed movie

Atom type Four-character code

Movie 'moov'

Compressed movie 'cmov'

Data compression atom 'dcom'

Compressed movie data 'cmvd'

32-bit integer Uncompressed size

Reference Movies

A QuickTime movie can act as a container for a set of alternate movies that should be displayed under
specified conditions. One of these movies may be contained within the same file; any others are
included by reference.

For example, a QuickTime movie can contain a list of references to movies having different data rates,
allowing an application to choose the best-looking movie that can play smoothly as it downloads
over the Internet, based on the user’s connection speed.

A movie that contains references to alternate movies is called a reference movie.

A reference movie contains a reference movie atom ('rmra') at the top level of the movie atom. The
movie atom may also contain a movie header atom, or it may contain the reference movie atom alone.

Figure 2-40 A movie atom containing a 'rmra' atom instead of a 'mvhd' atom

Movie atom

Atom size
Type = 'moov'

Reference movie atom 'rmra'

The reference movie atom contains one or more reference movie descriptor atoms, each of which
describes an alternate movie.

Each reference movie descriptor atom contains a data reference atom, which specifies the location of
a movie.

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Movie Atoms

Note: Movie locations are specified using QuickTime data references. QuickTime supports multiple
types of data reference, but alternate movies are generally specified using data reference types of
either url ('url ') or file alias ('alis').

A reference movie descriptor atom may contain other atoms that specify the movie’s system
requirements and the movie quality. If so, there will be an atom of an appropriate type for each
requirement that must be met for the movie to play, and there may be a quality atom as well.

Applications should play the highest-quality movie whose requirements are met by the user’s system.
If the data reference to the selected movie cannot be resolved—because the file cannot be found, for
example—the application should recursively attempt to play the next-highest-quality movie until it
succeeds or has exhausted the list of movies whose requirements are met.

If a movie contains both a reference movie atom and a movie header atom, applications should play
the appropriate movie indicated by the reference movie atom.

If the user’s system does not meet any of the alternate movies’ criteria, or none of the qualifying data
references can be resolved, applications should play the movie defined in the movie header atom.
(The movie defined in the movie header atom can also be indicated by one of the alternate movie
references.)

The movie header atom is sometimes used to provide a fallback movie for applications that can play
older QuickTime movies but do not understand reference movies.

Reference Movie Atom
A reference movie atom contains references to one or more movies. It can optionally contain a list of
system requirements in order for each movie to play, and a quality rating for each movie. It is typically
used to specify a list of alternate movies to be played under different conditions.

A reference movie atom’s parent is always a movie atom ('moov'). Only one reference movie atom
is allowed in a given movie atom.

A reference movie atom may contain the following information.

Size
The number of bytes in this reference movie atom.

Type
The type of this atom; this field must be set to 'rmra'.

Reference movie descriptor atom
A reference movie atom must contain at least one reference movie descriptor atom, and typically
contains more than one. See “Reference Movie Descriptor Atom” (page 86) for more
information.

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Movie Atoms

Figure 2-41 A ‘rmra’ atom with multiple ‘rmda’ atoms

Reference Movie atom

Atom size
Type = 'rmra'

Reference Movie Descriptor atom 'rmda'



Reference Movie Descriptor Atom
Each reference movie descriptor atom contains other atoms that describe where a particular movie
can be found, and optionally what the system requirements are to play that movie, as well as an
optional quality rating for that movie.

A reference movie descriptor atom’s parent is always a movie reference atom ('rmra'). Multiple
reference movie descriptor atoms are allowed in a given movie reference atom, and more than one
is usually present.

A reference movie descriptor atom may contain the following information.

Size
The number of bytes in this reference movie descriptor atom.

Type
The type of this atom; this field must be set to 'rmda'.

Data reference atom
Each reference movie atom must contain exactly one data reference atom. See “Data Reference
Atoms” (page 68) for more information.

Data rate atom
A reference movie atom may contain an optional data rate atom. Only one data rate atom can
be present. See “Data Rate Atom” (page 88) for more information.

CPU speed atom
A reference movie atom may contain an optional CPU speed atom. Only one CPU speed atom
can be present. See “CPU Speed Atom” (page 88) for more information.

Version check atom
A reference movie atom may contain an optional version check atom. Multiple version check
atoms can be present. See “Version Check Atom” (page 89) for more information.

Component detect atom
A reference movie atom may contain an optional component detect atom. Multiple component
detect atoms can be present. See “Component Detect Atom” (page 90) for more information.

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Movie Atoms

Quality atom
A reference movie atom may contain an optional quality atom. Only one quality atom can be
present. See “Quality Atom” (page 92) for more information.

Figure 2-42 Reference movie descriptor atom

Reference Movie Descriptor atom

Atom size
Type = 'rmda'

Data Reference atom 'rdrf'

Data Rate atom 'rmdr'
CPU Speed atom 'rmcs'

Version Check atom 'rmvc'

Component Detect atom 'rmcd'

Quality atom 'rmqu'

Data Reference Atom
A data reference atom contains the information necessary to locate a movie, or a stream or file that
QuickTime can play, typically in the form of a URL or a file alias.

Only one data reference atom is allowed in a given movie reference descriptor atom.

A data reference atom may contain the following information.

Size
The number of bytes in this data reference atom.

Type
The type of this atom; this field must be set to 'rdrf'.

Flags
A 32-bit integer containing flags. One flag is currently defined: movie is self-contained. If the
least-significant bit is set to 1, the movie is self-contained. This requires that the parent movie
contain a movie header atom as well as a reference movie atom. In other words, the current
'moov' atom must contain both a 'rmra' atom and a 'mvhd' atom. To resolve this data
reference, an application uses the movie defined in the movie header atom, ignoring the
remainder of the fields in this data reference atom, which are used only to specify external
movies.

Data reference type
The data reference type. A value of 'alis' indicates a file system alias record. A value of 'url
' indicates a string containing a uniform resource locator. Note that the fourth character in
'url ' is an ASCII blank (hex 20).

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Movie Atoms

Data reference size
The size of the data reference in bytes, expressed as a 32-bit integer.

Data reference
A data reference to a QuickTime movie, or to a stream or file that QuickTime can play. If the
reference type is 'alis' this field contains the contents of an AliasHandle. If the reference
type is 'url ' this field contains a null-terminated string that can be interpreted as a URL.
The URL can be absolute or relative, and can specify any protocol that QuickTime supports,
including http://, ftp://, rtsp://, file:///, and data:.

Data Rate Atom
A data rate atom specifies the minimum data rate required to play a movie. This is normally compared
to the connection speed setting in the user’s QuickTime Settings control panel. Applications should
play the movie with the highest data rate less than or equal to the user’s connection speed. If the
connection speed is slower than any movie’s data rate, applications should play the movie with the
lowest data rate. The movie with the highest data rate is assumed to have the highest quality.

Only one data rate atom is allowed in a given reference movie descriptor atom.

A data rate atom may contain the following information.

Size
The number of bytes in this data rate atom.

Type
The type of this atom; this field must be set to 'rmdr'.

Flags
A 32-bit integer that is currently always 0.

Data rate
The required data rate in bits per second, expressed as a 32-bit integer.

CPU Speed Atom
A CPU speed atom specifies the minimum computing power needed to display a movie. QuickTime
performs an internal test to determine the speed of the user’s computer.

This is not a simple measurement of clock speed—it is a measurement of performance for
QuickTime-related operations. Speed is expressed as a relative value between 100 and 2^31, in
multiples of 100.

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Movie Atoms

Note: Typical scores might range from a minimum score of 100, which would describe a computer
as slow as, or slower than, a 166 MHz Pentium or 120 MHz PowerPC, to a maximum score of 600 for
a 500 MHz Pentium III or 400 MHz G4 PowerPC. A computer with a graphics accelerator and a
Gigahertz clock speed might score as high as 1000. Future computers will score higher.

Applications should play the movie with the highest specified CPU speed that is less than or equal
to the user’s speed. If the user’s speed is lower than any movie’s CPU speed, applications should play
the movie with the lowest CPU speed requirement. The movie with the highest CPU speed is assumed
to be the highest quality.

Only one CPU speed atom is allowed in a given reference movie descriptor atom.

A CPU speed atom may contain the following information.

Size
The number of bytes in this CPU speed atom.

Type
The type of this atom; this field must be set to 'rmcs'.

Flags

CPU speed
A relative ranking of required computer speed, expressed as a 32-bit integer divisible by 100,
with larger numbers indicating higher speed.

Version Check Atom
A version check atom specifies a software package, such as QuickTime or QuickTime VR, and the
version of that package needed to display a movie. The package is specified using a Macintosh Gestalt
type, such a 'qtim' for QuickTime (QuickTime provides support for these Gestalt tests in the Windows
computing environment).

You can specify a minimum required version to be returned by the Gestalt check, or you can require
that a specific value be returned after performing a binary AND operation on the Gestalt bitfield and
a mask.

Multiple version check atoms are allowed within a given reference movie descriptor atom. Applications
should not attempt to play a movie unless all version checks are successful.

A version check atom may contain the following information.

Size
The number of bytes in this version check atom.

Type
The type of this atom; this field must be set to 'rmvc'.

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Movie Atoms

Flags

Software package
A 32-bit Gestalt type, such as 'qtim', specifying the software package to check for.

Version
An unsigned 32-bit integer containing either the minimum required version or the required
value after a binary AND operation.

Mask
The mask for a binary AND operation on the Gestalt bitfield.

Check type
The type of check to perform, expressed as 16-bit integer. Set to 0 for a minimum version check,
set to 1 for a required value after a binary AND of the Gestalt bitfield and the mask.

Component Detect Atom
A component detect atom specifies a QuickTime component, such as a particular video decompressor,
required to play the movie. The component type, subtype, and other required attributes can be
specified, as well as a minimum version.

Multiple component detect atoms are allowed within a given reference movie descriptor atom.
Applications should not attempt to play a movie unless at least the minimum versions of all required
components are present.

A component detect atom may contain the following information.

Size
The number of bytes in this component detect atom.

Type
The type of this atom; this field must be set to 'rmcd'.

Flags

Component description
A component description record. For details, see “Component Description Record” (page 90).

Minimum version
An unsigned 32-bit integer containing the minimum required version of the specified
component.

Component Description Record

Describes a class of components by their attributes. Fields that are set to 0 are treated as “don’t care.”

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Movie Atoms

struct ComponentDescription {
OSType componentType;
OSType componentSubType;
OSType componentManufacturer;
unsigned long componentFlags;
unsigned long componentFlagsMask;
};

componentType
A four-character code that identifies the type of component.

componentSubType
A four-character code that identifies the subtype of the component. For example, the subtype
of an image compressor component indicates the compression algorithm employed by the
compressor. A value of 0 matches any subtype.

componentManufacturer
A four-character code that identifies the manufacturer of the component. Components provided
by Apple have a manufacturer value of 'appl'. A value of 0 matches any manufacturer.

componentFlags
A 32-bit field that contains flags describing required component capabilities. The high-order
8 bits should be set to 0. The low-order 24 bits are specific to each component type. These flags
can be used to indicate the presence of features or capabilities in a given component.

componentFlagsMask
A 32-bit field that indicates which flags in the componentFlags field are relevant to this
operation. For each flag in the componentFlags field that is to be considered as a search criterion,
set the corresponding bit in this field to 1. To ignore a flag, set the bit to 0.

Constants
canMovieImportInPlace
Set this bit if a movie import component must be able to create a movie from a file without
having to write to a separate disk file. Examples include MPEG and AIFF import components.

movieImportSubTypeIsFileExtension
Set this bit if the component's subtype is a file extension instead of a Macintosh file type. For
example, if you require an import component that opens files with an extension of .doc, set
this flag and set your component subtype to 'DOC '.

canMovieImportFiles
Set this bit if a movie import component must import files.

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Movie Atoms

Quality Atom
A quality atom describes the relative quality of a movie. This acts as a tie-breaker if more than one
movie meets the specified requirements, and it is not otherwise obvious which movie should be
played.

This would be the case if two qualified movies have the same data rate and CPU speed requirements,
for example, or if one movie requires a higher data rate and another requires a higher CPU speed,
but both can be played on the current system. In these cases, applications should play the movie with
the highest quality, as specified in the quality atom.

Only one quality atom is allowed in a given reference movie descriptor atom.

A quality atom may contain the following information.

Size
The number of bytes in this quality atom.

Type
The type of this atom; this field must be set to 'rmqu'.

Quality
The relative quality of the movie, expressed as a 32-bit integer. A larger number indicates
higher quality. A unique value should be given to each movie.

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Media Data Atom Types

QuickTime uses atoms of different types to store different types of media data—video media atoms
for video data, sound media atoms for audio data, and so on. This chapter discusses in detail each of
these different media data atom types.

If you are a QuickTime application or tool developer, you’ll want to read this chapter in order to
understand the fundamentals of how QuickTime uses atoms for storage of different media data. The
information in this chapter is current as of QuickTime 4.1. For the latest updates and postings on
Apple’s QuickTime developer website, be sure to see
http://developer.apple.com/documentation/Quicktime/Quicktime.html.

This chapter is divided into the following major sections:

■ “Video Media” (page 94) describes video media, which is used to store compressed and
uncompressed image data in QuickTime movies.
■ “Sound Media” (page 101) discusses sound media used to store compressed and uncompressed
audio data in QuickTime movies.
■ “Timecode Media” (page 108) describes time code media used to store time code data in QuickTime
movies.
■ “Text Media” (page 111) discusses text media used to store text data in QuickTime movies.
■ “Music Media” (page 115) discusses music media used to store note-based audio data, such as
MIDI data, in QuickTime movies.
■ “MPEG Media” (page 115) discusses MPEG media used to store MPEG streams in QuickTime
movies.
■ “Sprite Media” (page 116) discusses sprite media used to store character-based animation data in
QuickTime movies.
■ “Tween Media” (page 136) discusses tween media used to store pairs of values to be interpolated
between in QuickTime movies.
■ “Modifier Tracks” (page 145) discusses the capabilities of modifier tracks.
■ “Track References” (page 146) describes a feature of QuickTime that allows you to relate a movie’s
tracks to one another.
■ “3D Media” (page 147) discusses briefly how QuickTime movies store 3D image data in a base
media.
■ “Hint Media” (page 148) describes the additions to the QuickTime file format for streaming
QuickTime movies over the Internet.

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■ “VR Media” (page 163) describes the QuickTime VR world and node information atom containers,
as well as cubic panoramas, which are new to QuickTime VR 3.0.
■ “Movie Media” (page 197) discusses movie media which is used to encapsulate embedded movies
within QuickTime movies.

Video Media

Video media is used to store compressed and uncompressed image data in QuickTime movies. It has
a media type of 'vide'.

Video Sample Description
The video sample description contains information that defines how to interpret video media data.
This sample description is based on the standard sample description, as described in “Sample
Description Atoms” (page 72).

The data format field of a video sample description indicates the type of compression that was used
to compress the image data. Table 3-1 (page 94) shows some of the formats supported.

Table 3-1 Some image compression formats

Compression type Description

'cvid' Cinepak

'jpeg' JPEG

'raw ' Uncompressed RGB

'Yuv2' Uncompressed YUV422

'smc ' Graphics

'rle ' Animation

'rpza' Apple video

'kpcd' Kodak Photo CD

'mpeg' MPEG

'mjpa' Motion-JPEG (format A)

'mjpb' Motion-JPEG (format B)

'svqi' Sorenson video

The video media handler also adds some of its own fields to the sample description.

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Version
A 16-bit integer indicating the version number of the compressed data. This is set to 0, unless
a compressor has changed its data format.

Revision level

Vendor
A 32-bit integer that specifies the developer of the compressor that generated the compressed
data. Often this field contains 'appl' to indicate Apple Computer, Inc.

Temporal quality
A 32-bit integer containing a value from 0 to 1023 indicating the degree of temporal compression.

Spatial quality
A 32-bit integer containing a value from 0 to 1024 indicating the degree of spatial compression.

Width
A 16-bit integer that specifies the width of the source image in pixels.

Height
A 16-bit integer that specifies the height of the source image in pixels.

Horizontal resolution
A 32-bit fixed-point number containing the horizontal resolution of the image in pixels per
inch.

Vertical resolution
A 32-bit fixed-point number containing the vertical resolution of the image in pixels per inch.

Data size

Frame count
A 16-bit integer that indicates how many frames of compressed data are stored in each sample.
Usually set to 1.

Compressor name
A 32-byte Pascal string containing the name of the compressor that created the image, such as
”jpeg”.

Depth
A 16-bit integer that indicates the pixel depth of the compressed image. Values of 1, 2, 4, 8 ,16,
24, and 32 indicate the depth of color images. The value 32 should be used only if the image
contains an alpha channel. Values of 34, 36, and 40 indicate 2-, 4-, and 8-bit grayscale,
respectively, for grayscale images.

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Color table ID
A 16-bit integer that identifies which color table to use. If this field is set to –1, the default color
table should be used for the specified depth. For all depths below 16 bits per pixel, this indicates
a standard Macintosh color table for the specified depth. Depths of 16, 24, and 32 have no color
table.
If the color table ID is set to 0, a color table is contained within the sample description itself.
The color table immediately follows the color table ID field in the sample description. See
“Color Table Atoms” (page 35) for a complete description of a color table.

Video sample descriptions can be extended by appending other atoms. These atoms are placed after
the color table, if one is present. These extensions to the sample description may contain display hints
for the decompressor or may simply carry additional information associated with the images. Table
3-2 (page 96) lists the currently defined extensions to video sample descriptions.

Table 3-2 Video sample description extensions

Extension
Description
type

'gama' A 32-bit fixed-point number indicating the gamma level at which the
image was captured. The decompressor can use this value to
gamma-correct at display time.

'fiel' Two 8-bit integers that define field handling. This information is used
by applications to modify decompressed image data or by
decompressor components to determine field display order.The first
byte specifies the field count, and may be set to 1 or 2. When the field
count is 2, the second byte specifies the field ordering: which contains
the topmost scan-line, which field should be displayed earliest, and
which is stored first in each sample. Each QuickTime sample consists
of two distinct compressed images, each coding one field: the field
with the topmost scan-line, T, and the other field, B. Each field is half
the height of the overall image, as declared in the height field of the
sample description. To be precise, if the height field contains the
value H, then the field T has ((H+1) div 2) lines, and field B has (H
div 2) lines. The following defines the permitted variants:0 – field
ordering is unknown. 1 – T is displayed earliest, T is stored first in
the file. 6 – B is displayed earliest, B is stored first in the file.

'mjqt' The default quantization table for a Motion-JPEG data stream.

'mjht' The default Huffman table for a Motion-JPEG data stream.

Video Sample Data
The format of the data stored in video samples is completely dependent on the type of the compressed
data stored in the video sample description. The following sections discuss each of the video encoding
schemes supported by QuickTime.

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Uncompressed RGB

Uncompressed RGB data is stored in a variety of different formats. The format used depends on the
depth field of the video sample description. For all depths, the image data is padded on each scan
line to ensure that each scan line begins on an even byte boundary.

■ For depths of 1, 2, 4, and 8, the values stored are indexes into the color table specified in the color
table ID field.
■ For a depth of 16, the pixels are stored as 5-5-5 RGB values with the high bit of each 16-bit integer
set to 0.
■ For a depth of 24, the pixels are stored packed together in RGB order.
■ For a depth of 32, the pixels are stored with an 8-bit alpha channel, followed by 8-bit RGB
components.

Uncompressed yuv2

The yuv2 stream is encoded in a series of 4-byte packets. Each packet represents two adjacent pixels
on the same scan line. The bytes within each packet are ordered as follows:

y0 u y1 v

y0 is the luminance value for the left pixel; y1 the luminance for the right pixel. u and v are chromatic
values that are shared by both pixels. The conversion into RGB space is represented by the following
equations:

r = 1.402 * v + y + .5

g = y - .7143 * v - .3437 * u + .5

b = 1.77 * u + y + .5

The r, g, and b values range from 0 to 255.

JPEG

QuickTime stores JPEG images according to the rules described in the ISO JPEG specification, document
number DIS 10918-1.

Motion-JPEG

Motion-JPEG (M-JPEG) is a variant of the ISO JPEG specification for use with digital video streams.
Instead of compressing an entire image into a single bitstream, Motion-JPEG compresses each video
field separately, returning the resulting JPEG bitstreams consecutively in a single frame.

There are two flavors of Motion-JPEG currently in use. These two formats differ based on their use
of markers. Motion-JPEG format A supports markers; Motion-JPEG format B does not. The following
paragraphs describe how QuickTime stores Motion-JPEG sample data. Figure 3-1 (page 100) shows
an example of Motion-JPEG A dual-field sample data. Figure 3-2 (page 101) shows an example of
Motion- JPEG B dual-field sample data.

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Each field of Motion-JPEG format A fully complies with the ISO JPEG specification, and therefore
supports application markers. QuickTime uses the APP1 marker to store control information, as
follows (all of the fields are 32-bit integers):

Reserved
Unpredictable; should be set to 0.

Tag
Identifies the data type; this field must be set to 'mjpg'.

Field size
The actual size of the image data for this field, in bytes.

Padded field size
Contains the size of the image data, including pad bytes. Some video hardware may append
pad bytes to the image data; this field, along with the field size field, allows you to compute
how many pad bytes were added.

Offset to next field
The offset, in bytes, from the start of the field data to the start of the next field in the bitstream.
This field should be set to 0 in the last field’s marker data.

Quantization table offset
The offset, in bytes, from the start of the field data to the quantization table marker. If this field
is set to 0, check the image description for a default quantization table.

Huffman table offset
The offset, in bytes, from the start of the field data to the Huffman table marker. If this field is
set to 0, check the image description for a default Huffman table.

Start Of Frame offset
The offset from the start of the field data to the start of image marker. This field should never
be set to 0.

Start Of Scan offset
The offset, in bytes, from the start of the field data to the start of the scan marker. This field
should never be set to 0.

Start of data offset
The offset, in bytes, from the start of the field data to the start of the data stream. Typically,
this immediately follows the start of scan data.

Note: The last two fields have been added since the original Motion-JPEG specification, and so they
may be missing from some Motion-JPEG A files. You should check the length of the APP1 marker
before using the Start Of Scan offset and Start of data offset fields. u

Motion-JPEG format B does not support markers. In place of the marker, therefore, QuickTime inserts
a header at the beginning of the bitstream. Again, all of the fields are 32-bit integers.

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Reserved
Unpredictable; should be set to 0.

Tag
The data type; this field must be set to 'mjpg'.

Field size
The actual size of the image data for this field, in bytes.

Padded field size
The size of the image data, including pad bytes. Some video hardware may append pad bytes
to the image data; this field, along with the field size field, allows you to compute how many
pad bytes were added.

Offset to next field
The offset, in bytes, from the start of the field data to the start of the next field in the bitstream.
This field should be set to 0 in the second field’s header data.

Quantization Table offset
The offset, in bytes, from the start of the field data to the quantization table. If this field is set
to 0, check the image description for a default quantization table.

Huffman Table offset
The offset, in bytes, from the start of the field data to the Huffman table. If this field is set to
0, check the image description for a default Huffman table.

The offset from the start of the field data to the field’s image data. This field should never be
set to 0.

Start Of Scan offset
The offset, in bytes, from the start of the field data to the start of scan data.

Start of data offset
The offset, in bytes, from the start of the field data to the start of the data stream. Typically,
this immediately follows the start of scan data.

Note: The last two fields were “reserved, must be set to zero” in the original Motion-JPEG specification.
u

The Motion-JPEG format B header must be a multiple of 16 in size. When you add pad bytes to the
header, set them to 0.

Because Motion-JPEG format B does not support markers, the JPEG bitstream does not have null
bytes (0x00) inserted after data bytes that are set to 0xFF.

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Figure 3-1 Motion-JPEG A dual-field sample data

First field
in sample JPEG Start Of Image marker FF D8

(Other markers, for example JFIF )
Motion-JPEG APP1 marker FF E1
Marker content length 00 2A
Reserved, set to zero 00 00 00 00

Motion-JPEG tag 'mjpg' 6D 6A 70 67
Field size
Byte
offsets Padded field size
from
start Offset to next field
of
field Quantization table offset


Start Of Scan offset (or zero) Not in original
Motion-JPEG
Start of data offset (or zero) A specification
Other markers
JPEG DQT marker FF DB 00 84 .. ..
JPEG DHT marker FF C4 01 A2 .. ..

JPEG SOF marker FF C0 00 11 .. ..
JPEG SOS marker FF DA 00 0C
JPEG entropy-coded data .. .. .. ..
JPEG EOI marker FF D9
Optional padding with FFs FF FF FF
Second field JPEG Start Of Image marker FF D8
in sample

Motion-JPEG APP1 marker

Offset to next field, zero 00 00 00 00

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Figure 3-2 Motion-JPEG B dual-field sample data

First field in sample
Motion-JPEG marker (no header)

Reserved, set to zero 00 00 00 00

Motion-JPEG tag 'mjpg' 6D 6A 70 67

Field size
Byte
offsets
Padded field size
from
start
of Offset to next field
field
Quantization table offset



Start Of Scan offset (or zero)

Start of data offset (or zero)

Padding with zeros to 16-byte boundary 00 00

Quantization table data 00 84

Optional padding with zeros 00 00 .. ..

Huffman table data 01 A2 .. ..

Start Of Frame data 00 11 .. ..

Start Of Scan data 00 0C .. ..

JPEG entropy-coded data a (not byte-stuffed) .. .. .. ..

Padding with zeros to 16-byte boundary 00 00 00

Second field in sample
Motion JPEG marker

Offset to next field, zero 00 00 00 00

Sound Media

Sound media is used to store compressed and uncompressed audio data in QuickTime movies. It has
a media type of 'soun'.

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Sound Sample Description
The sound sample description contains information that defines how to interpret sound media data.
This sample description is based on the standard sample description, as described in “Sample

The data format field contains the format of the audio data. Table 3-3 (page 105) shows a list of
supported sound codec formats.

The sound media handler also adds some of its own fields to the sample description.

Version
A 16-bit integer that must be set to 0 or 1 (see below).

Revision level

Vendor

Number of channels
A 16-bit integer that indicates the number of sound channels used by the sound sample. Set
this field to 1 for monaural sounds; set it to 2 for stereo sounds.

Sample size
A 16-bit integer that specifies the number of bits in each uncompressed sound sample. Set this
field to 8 for 8-bit sound, and to 16 for 16-bit sound.

Compression ID
A 16-bit integer that must be set to 0 (or, for version 1, may be -2. See below).

Packet size

Sample rate
A 32-bit unsigned fixed-point number that indicates the rate at which the sound samples were
obtained. This number should match the media’s time scale, that is, the integer portion should
match.

Variants of the Sample Description

A QuickTime sound sample description describes the format of a collection of audio samples. There
are, however, three variants of the sound sample description.

Initially, QuickTime defined a sample of sound as an uncompressed sample, not, as in other tracks,
a compressed sample. In any codec that operated on frames of audio (for example, the 20 millisecond
frame common in telephony), it was necessary to determine how many uncompressed samples were
in a frame, how many bytes that compressed to, and the size of the resulting uncompressed samples.
This information was classically retrieved from the sound decompressor component. The sample
tables (sample to time, sample size) were very compact, as they documented uncompressed samples.

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Version 0 of the sound description format assumes that this is the case.

In version 1 of the sound description, introduced in QuickTime 3, the record is extended by 4 fields,
each 4 bytes long, storing data that could otherwise have only been retrieved from the decompressor.
This enables operating on the file in the absence of the decompressor component.

These added fields are used to support compression algorithms that can be run at different compression
ratios, and to support more generic parsing of QuickTime sound tracks, that is, it allows the parsing
without requiring the particular to be available.

The version field is set to 1 to indicate this new format. The four fields are:

■ samples per packet––the number of uncompressed samples in a packet
■ bytes per packet––the resulting compressed number of bytes for one channel
■ bytes per frame––the resulting compressed number of bytes for all channels (channels * bytes per
packet)
■ bytes per sample––the size of an uncompressed sample

In both formats, version 0 and version 1, the timescale of the track is set to the sampling rate.

In many respects, version 1 of the SoundDescription record is a superset of the version 0 sound
description. The new fields are taken directly from the CompressionInfo structure used by the Sound
Manager (which uses 16-bit values) to describe the compression ratio of fixed ratio audio compression
algorithms. If these fields are not used, they are set to 0. File readers only need to check to see if
samplesPerPacket is 0.

Version 1 also defines how extensions are added to the SoundDescription record.

struct SoundDescriptionV1 {
// original fields
SoundDescription desc;
// fixed compression ratio information
unsigned long samplesPerPacket;
unsigned long bytesPerPacket;
unsigned long bytesPerFrame;
unsigned long bytesPerSample;
// optional, additional atom-based fields --
// ([long size, long type, some data], repeat)
};

All other additions to the SoundDescription record are made using QT atoms. That means one or
more atoms can be appended to the end of the SoundDescription record using the standard [size,
type] mechanism used throughout the QuickTime movie resource architecture.

Two extensions are defined to the SoundDescription record. The second extension provides the
ability to store data specific to a given audio decompressor in the SoundDescription record. Some
audio decompression algorithms, such as Microsoft’s ADPCM, require a set of out-of-band values to
configure the decompressor. These are stored in an atom of type siDecompressorSettings. The
contents of the siDecompressorSettings atom are dependent on the audio decompressor. If the
QuickTime movie is created from a WAVE (.WAV) or AVI (.avi) file, the siDecompressorSettings
atom is automatically created and set to the contents of the WAVEFORMATEX structure from that file. In
this case, the siDecompressorSettings atom contains little-endian data.

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At runtime, the contents of the type siSlopeAndIntercept and siDecompressorSettings atoms
are provided to the decompressor component through the standard SetInfo mechanism of the Sound
Manager.

The first extension to the SoundDescription record is the slope, intercept, minClip, and maxClip
parameters for audio. This is represented as an atom of type siSlopeAndIntercept. The contents
of the atom are

struct SoundSlopeAndInterceptRecord {
Float64 slope;
Float64 intercept;
Float64 minClip;
Float64 maxClip;
};
typedef struct SoundSlopeAndInterceptRecord SoundSlopeAndInterceptRecord;

VBR Audio (the Third Variant)

With the introduction of support for the playback of variable bit-rate (VBR) audio in QuickTime 4.1,
the meaning of a number of fields has changed. (Previous versions of QuickTime supported only
constant bit-rate (CBR) audio, while a number of modern audio compression formats––such as
MP3––either support or require VBR encoding.)

In particular, a sample in a VBR audio track is, in QuickTime 4.1, a compressed frame of audio. The
sample table documents these frames; specifically, the sample size table documents the size of the
frames. This is constant for CBR audio, but varies for VBR.

The time to sample table documents the duration of the frames. Since the timescale is set to the
sampling rate, this indicates the number of uncompressed samples in each packet, which is usually
constant, even for VBR (it is common to use a fixed frame duration), though not required.

To indicate that this new meaning is used, a version 1 sound description is used and the compression
ID field is set to -2. The samples per packet should be set correctly, if it is constant, as should the bytes
per sample; the other two new fields are reserved and should be set to 0.

Sound Sample Data
The format of data stored in sound samples is completely dependent on the type of the compressed
data stored in the sound sample description. The following sections discuss each of the formats
supported by QuickTime.

Sound Codec Formats Supported
The sound codec formats shown in Table 3-3 (page 105) are typical of the different forms of
uncompressed audio supported in QuickTime. Note that the 16-bit forms come in both big- and
little-endian forms.

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Table 3-3 Supported QuickTime audio formats. Note that not all of these are uncompressed.

4-Character
Format Description
code

kSoundNotCompressed 'NONE' Sound is not compressed

k8BitOffsetBinaryFormat 'raw ' Samples are stored uncompressed,
in offset-binary format (values
range from 0 to 255; 128 is silence).
These are stored as 8-bit offset
binaries.

k16BitBigEndianFormat 'twos' Samples are stored uncompressed,
in two’s-complement format
(sample values range from -128 to
127 for 8-bit audio, and -32768 to
32767 for 1- bit audio; 0 is always
silence). These samples are stored
in 16-bit big-endian format.

k16BitLittleEndianFormat 'sowt' 16-bit little-endian,
twos-complement

kMACE3Compression 'MAC3 ' Samples have been compressed
using MACE 3:1. (Obsolete.)

kMACE6Compression 'MAC6 ' Samples have been compressed
using MACE 6:1. (Obsolete.)

kIMACompression 'ima4 ' Samples have been compressed
using IMA 4:1.

kFloat32Format 'fl32' 32-bit floating point

kFloat64Format 'fl64' 64-bit floating point

k24BitFormat 'in24' 24-bit integer

k32BitFormat 'in32' 32-bit integer

kULawCompression 'ulaw' uLaw 2:1

kALawCompression 'alaw' uLaw 2:1

kMicrosoftADPCMFormat 0x6D730002 Microsoft ADPCM-ACM code 2

kDVIIntelIMAFormat 0x6D730011 DVI/Intel IMAADPCM-ACM code
17

kDVAudioFormat 'dvca' DV Audio

kQDesignCompression 'QDMC' QDesign music

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4-Character
Format Description
code

unnamed 'QDM2' QDesign music version 2 (no
constant).

kQUALCOMMCompression 'Qclp' QUALCOMM PureVoice

kMPEGLayer3Format 0x6D730055 MPEG layer 3, CBR only (pre-
QT4.1)

kFullMPEGLay3Format '.mp3' MPEG layer 3, CBR & VBR (QT4.1
and later)

Uncompressed 8-Bit Sound

Eight-bit audio is stored in offset-binary encodings. If the data is in stereo, the left and right channels
are interleaved.

Uncompressed 16-Bit Sound

Sixteen-bit audio may be stored in two’s-complement encodings. If the data is in stereo, the left and
right channels are interleaved.

IMA, uLaw, and aLaw

The following are formats currently not in use:

■ IMA 4:1
The IMA encoding scheme is based on a standard developed by the International Multimedia
Assocation for pulse code modulation (PCM) audio compression. QuickTime uses a slight variation
of the format to allow for random access. IMA is a 16-bit audio format which supports 4:1
compression. It is defined as follows:

kIMACompression = FOUR_CHAR_CODE('ima4'), /*IMA 4:1*/

■ uLaw 2:1 and aLaw 2:1
The uLaw (mu-law) encoding scheme is used on North American and Japanese phone systems,
and is coming into use for voice data interchange, and in PBXs, voice-mail systems, and Internet
talk radio (via MIME). In uLaw encoding, 14 bits of linear sample data are reduced to 8 bits of
logarithmic data.
The aLaw encoding scheme is used in Europe and the rest of the world.
The kULawCompression and the kALawCompression formats are typically found in .au formats.

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Floating-Point Formats

Both kFloat32Format and kFloat64Format are floating-point uncompressed formats. Depending upon
codec-specific data associated with the sample description, the floating-point values may be in
big-endian (network) or little-endian (Intel) byte order. This differs from the 16-bit formats, where
there is a single format for each endia layout.

24- and 32-Bit Integer Formats

Both k24BitFormat and k32BitFormat are integer uncompressed formats. Depending upon
codec-specific data associated with the sample description, the floating-point values may be in
big-endian (network) or little-endian (Intel) byte order.

kMicrosoftADPCMFormat and kDVIIntelIMAFormat Sound
Codecs

The kMicrosoftADPCMFormat and the kDVIIntelIMAFormat codec provide QuickTime interoperability
with AVI and WAV files. The four-character codes used by Microsoft for their formats are numeric.
To construct a QuickTime-supported codec format of this type, the Microsoft numeric ID is taken to
generate a four-character code of the form 'msxx' where xx takes on the numeric ID.

kDVAudioFormat Sound Codec

The DV audio sound codec, kDVAudioFormat, decodes audio found in a DV stream. Since a DV
frame contains both video and audio, this codec knows how to skip video portions of the frame and
only retrieve the audio portions. Likewise, the video codec skips the audio portions and renders only
the image.

kQDesignCompression Sound Codec

The kQDesignCompression sound codec is the QDesign 1 (pre-QuickTime 4) format. Note that there
is also a QDesign 2 format whose four-character code is 'QDM2'.

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MPEG Layer 3 (MP3) Codecs

The QuickTime MPEG layer 3 (MP3) codecs come in two particular flavors, as shown in Table
3-3 (page 105). The first (kMPEGLayer3Format) is used exclusively in the constant bitrate (CBR) case
(pre-QuickTime 4). The other (kFullMPEGLay3Format) is used in both the CBR and variable bitrate
(VBR) cases. Note that they are the same codec underneath.

Formats Not Currently in Use:MACE 3:1 and 6:1

These compression formats are obsolete: MACE 3:1 and 6:1.

These are 8-bit sound codec formats, defined as follows:

kMACE3Compression = FOUR_CHAR_CODE('MAC3'), /*MACE 3:1*/
kMACE6Compression = FOUR_CHAR_CODE('MAC6'), /*MACE 6:1*/

Timecode Media

Timecode media is used to store time code data in QuickTime movies. It has a media type of 'tmcd'.

Timecode Sample Description
The timecode sample description contains information that defines how to interpret time code media
data. This sample description is based on the standard sample description header, as described in
“Sample Description Atoms” (page 72).

The data format field in the sample description is always set to 'tmcd'.

The timecode media handler also adds some of its own fields to the sample description.

Reserved
A 32-bit integer that is reserved for future use. Set this field to 0.

Flags
A 32-bit integer containing flags that identify some timecode characteristics. The following
flags are defined.
Drop frame

Indicates whether the timecode is drop frame. Set it to 1 if the timecode is drop frame. This
flag’s value is 0x0001.

24 hour max

Indicates whether the timecode wraps after 24 hours. Set it to 1 if the timecode wraps. This

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Negative times OK

Indicates whether negative time values are allowed. Set it to 1 if the timecode supports negative
values. This flag’s value is 0x0004.

Counter

Indicates whether the time value corresponds to a tape counter value. Set it to 1 if the timecode
values are tape counter values. This flag’s value is 0x0008.

Time scale
A 32-bit integer that specifies the time scale for interpreting the frame duration field.

Frame duration
A 32-bit integer that indicates how long each frame lasts in real time.

Number of frames
An 8-bit integer that contains the number of frames per second for the timecode format. If the
time is a counter, this is the number of frames for each counter tick.

Reserved
A 24-bit quantity that must be set to 0.

Source reference
A user data atom containing information about the source tape. The only currently used user
data list entry is the 'name' type. This entry contains a text item specifying the name of the
source tape.

Timecode Media Information Atom
The timecode media also requires a media information atom. This atom contains information governing
how the timecode text is displayed. This media information atom is stored in a base media information
atom (see “Base Media Information Atoms” (page 64) for more information). The type of the timecode
media information atom is 'tcmi'.

The timecode media information atom contains the following data elements.

Size
A 32-bit integer that specifies the number of bytes in this time code media information atom.

Type
A 32-bit integer that identifies the atom type; this field must be set to 'tcmi'.

Version
A 1-byte specification of the version of this timecode media information atom.

Flags
A 3-byte space for timecode media information flags. Set this field to 0.

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Text font
A 16-bit integer that indicates the font to use. Set this field to 0 to use the system font. If the
font name field contains a valid name, ignore this field.

Text face
A 16-bit integer that indicates the font’s style. Set this field to 0 for normal text. You can enable
other style options by using one or more of the following bit masks:
0x0001 Bold

0x0002 Italic

0x0004 Underline

0x0008 Outline

0x0010 Shadow

0x0020 Condense

0x0040 Extend

Text size
A 16-bit integer that specifies the point size of the time code text.

Text color
A 48-bit RGB color value for the timecode text.

Background color
A 48-bit RGB background color for the timecode text.

Font name
A Pascal string specifying the name of the timecode text’s font.

Timecode Sample Data

There are two different sample data formats used by timecode media.

If the Counter flag is set to 1 in the timecode sample description, the sample data is a counter value.
Each sample contains a 32-bit integer counter value.

If the Counter flag is set to 0 in the timecode sample description, the sample data format is a timecode
record, as follows.

Hours
An 8-bit unsigned integer that indicates the starting number of hours.

Negative
A 1-bit value indicating the time’s sign. If bit is set to 1, the timecode record value is negative.

Minutes
A 7-bit integer that contains the starting number of minutes.

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Seconds
An 8-bit unsigned integer indicating the starting number of seconds.

Frames
An 8-bit unsigned integer that specifies the starting number of frames. This field’s value cannot
exceed the value of the number of frames field in the timecode sample description.

Text Media

Text media is used to store text data in QuickTime movies. It has a media type of 'text'.

Text Sample Description
The text sample description contains information that defines how to interpret text media data. This
sample description is based on the standard sample description header, as described in “Sample

The data format field in the sample description is always set to 'text'.

The text media handler also adds some of its own fields to the sample description.

Display flags
A 32-bit integer containing flags that describe how the text should be drawn. The following
flags are defined.
Don’t auto scale

Controls text scaling. If this flag is set to 1, the text media handler reflows the text instead of
scaling when the track is scaled. This flag’s value is 0x0002.

Use movie background color

Controls background color. If this flag is set to 1, the text media handler ignores the background
color field in the text sample description and uses the movie’s background color instead. This

Scroll in

Controls text scrolling. If this flag is set to 1, the text media handler scrolls the text until the
last of the text is in view. This flag’s value is 0x0020.

Scroll out

Controls text scrolling. If this flag is set to 1, the text media handler scrolls the text until the
last of the text is gone. This flag’s value is 0x0040.

Horizontal scroll

Controls text scrolling. If this flag is set to 1, the text media handler scrolls the text horizontally;
otherwise, it scrolls the text vertically. This flag’s value is 0x0080.

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Reverse scroll

Controls text scrolling. If this flag is set to 1, the text media handler scrolls down (if scrolling
vertically) or backward (if scrolling horizontally; note that horizontal scrolling also depends
upon text justification). This flag’s value is 0x0100.

Continuous scroll

Controls text scrolling. If this flag is set to 1, the text media handler displays new samples by
scrolling out the old ones. This flag’s value is 0x0200.

Drop shadow

Controls drop shadow. If this flag is set to1, the text media handler displays the text with a
drop shadow. This flag’s value is 0x1000.

Anti-alias

Controls anti-aliasing. If this flag is set to 1, the text media handler uses anti-aliasing when
drawing text. This flag’s value is 0x2000.

Key text

Controls background color. If this flag is set to 1, the text media handler does not display the
background color, so that the text overlay background tracks. This flag’s value is 0x4000.

Text justification
A 32-bit integer that indicates how the text should be aligned. Set this field to 0 for left-justified
text, to 1 for centered text, and to –1 for right-justified text.

Background color
A 48-bit RGB color that specifies the text’s background color.

Default text box
A 64-bit rectangle that specifies an area to receive text (top, left, bottom, right). Typically this
field is set to all zeros.

Reserved
A 64-bit value that must be set to 0.

Font number

Font face
A 16-bit integer that indicates the font’s style. Set this field to 0 for normal text. You can enable
other style options by using one or more of the following bit masks:
0x0001 Bold

0x0002 Italic

0x0004 Underline

0x0008 Outline

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0x0010 Shadow

0x0020 Condense

0x0040 Extend

Reserved
An 8-bit value that must be set to 0.

Reserved

Foreground color
A 48-bit RGB color that specifies the text’s foreground color.

Text name
A Pascal string specifying the name of the font to use to display the text.

Text Sample Data
The format of the text data is a 16-bit length word followed by the actual text. The length word specifies
the number of bytes of text, not including the length word itself. Following the text, there may be one
or more atoms containing additional information for drawing and searching the text.

Table 3-4 (page 113) lists the currently defined text sample extensions.

Table 3-4 Text sample extensions

Text sample
Description
extension

'styl' Style information for the text. Allows you to override the default
style in the sample description or to define more than one style for
a sample. The data is a TextEdit style scrap.

'ftab' Table of font names. Each table entry contains a font number (stored
in a 16-bit integer) and a font name (stored in a Pascal string).This
atom is required if the 'styl' atom is present.

'hlit' Highlight information. The atom data consists of two 32-bit integers.
The first contains the starting offset for the highlighted text, and
the second has the ending offset. A highlight sample can be in a key
frame or in a differenced frame. When it’s used in a differenced
frame, the sample should contain a zero-length piece of text.

'hclr' Highlight color. This atom specifies the 48-bit RGB color to use for
highlighting.

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Text sample
Description
extension

'drpo' Drop shadow offset. When the display flags indicate drop shadow
style, this atom can be used to override the default drop shadow
placement. The data consists of two 16-bit integers. The first
indicates the horizontal displacement of the drop shadow, in pixels;
the second, the vertical displacement.

'drpt' Drop shadow transparency. The data is a 16-bit integer between 0
and 256 indicating the degree of transparency of the drop shadow.
A value of 256 makes the drop shadow completely opaque.

'imag' Image font data. This atom contains two more atoms. An 'idat'
atom contains compressed image data to be used to draw the text
when the required fonts are not available. An 'idsc' atom contains
a video sample description describing the format of the compressed
image data.

'metr' Image font highlighting. This atom contains metric information that
governs highlighting when an'imag' atom is used for drawing.

Hypertext
Hypertext is used as an action that takes you to a Web URL; like a Web URL, it appears blue and
underlined. Hypertext is stored in a text track sample atom stream as type 'htxt'.

The data stored is a QTAtomContainer. The root atom of hypertext in this container is of type 'wtxt'.
This is the parent for all individual hypertext objects.

For each hypertext item, the parent atom is of type 'htxt'. This is the atom container atom type. Two
children of this atom that define the offset of the hypertext in the text stream are

kRangeStart strt // unsigned long
kRangeEnd end // unsigned long

Child atoms of the parent atom are the events of type kQTEventType and the ID of the event type.
The children of these event atoms follow the same format as other wired events.

kQTEventType, (kQTEventMouseClick, kQTEventMouseClickEnd,
kQTEventMouseClickEndTriggerButton,
kQTEventMouseEnter, kQTEventMouseExit)
...
kTextWiredObjectsAtomType, 1
kHyperTextItemAtomType, 1..n
kRangeStart, 1
long
kRangeEnd, 1
long

kAction // The known range of track movie sprite actions

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Music Media

Music media is used to store note-based audio data, such as MIDI data, in QuickTime movies. It has
a media type of 'musi'.

Music Sample Description
The music sample description uses the standard sample description header, as described in the section
“Sample Description Atoms” (page 72).

The data format field in the sample description is always set to 'musi'. The music media handler
adds an additional 32-bit integer field to the sample description containing flags. Currently no flags
are defined, and this field should be set to 0.

Following the flags field, there may be appended data in the QuickTime music format. This data
consists of part-to-instrument mappings in the form of General events containing note requests. One
note request event should be present for each part that will be used in the sample data.

Music Sample Data
The sample data for music samples consists entirely of data in the QuickTime music format. Typically,
up to 30 seconds of notes are grouped into a single sample. For a complete description of the QuickTime
music format, see your most recent QuickTime developer documentation.

MPEG Media

MPEG media is used to store MPEG streams in QuickTime movies. It has a media type of 'MPEG'.

MPEG Sample Description
The MPEG sample description uses the standard sample description header, as described in “Sample

The data format field in the sample description is always set to 'MPEG'. The MPEG media handler
adds no additional fields to the sample description.

MPEG Sample Data
Each sample in an MPEG media is an entire MPEG stream. This means that a single MPEG sample
may be several hundred megabytes in size. The MPEG encoding used by QuickTime corresponds to
the ISO standard, as described in ISO document CD 11172.

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Sprite Media

Sprite media is used to store character-based animation data in QuickTime movies. It has a media
type of 'sprt'.

Sprite Sample Description
The sprite sample description uses the standard sample description header, as described in “Sample

The data format field in the sample description is always set to 'sprt'. The sprite media handler

Sprite Sample Data
All sprite samples are stored in QT atom structures. The sprite media uses both key frames and
differenced frames. The key frames contain all of the sprite’s image data, and the initial settings for
each of the sprite’s properties.

A key frame always contains a shared data atom of type 'dflt'. This atom contains data to be shared
between the sprites, consisting mainly of image data and sample descriptions. The shared data atom
contains a single sprite image container atom, with an atom type value of 'imct' and an ID value of
1.

The sprite image container atom stores one or more sprite image atoms of type 'imag'. Each sprite
image atom contains an image sample description immediately followed by the sprite’s compressed
image data. The sprite image atoms should have ID numbers starting at 1 and counting consecutively
upward.

The key frame also must contain definitions for each sprite in atoms of type 'sprt'. Sprite atoms
should have ID numbers start at 1 and count consecutively upward. Each sprite atom contains a list
of properties. Table 3-5 (page 117) shows all currently defined sprite properties.

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Table 3-5 Sprite properties

Property name Value Description

kSpritePropertyMatrix 1 Describes the sprite’s location and scaling
within its sprite world or sprite track. By
modifying a sprite’s matrix, you can
modify the sprite’s location so that it
appears to move in a smooth path on the
screen or so that it jumps from one place
to another. You can modify a sprite’s size,
so that it shrinks, grows, or stretches.
Depending on which image compressor
is used to create the sprite images, other
transformations, such as rotation, may be
supported as well. Translation-only
matrices provide the best performance.

kSpritePropertyVisible 4 Specifies whether or not the sprite is
visible. To make a sprite visible, you set
the sprite’s visible property to true.

kSpritePropertyLayer 5 Contains a 16-bit integer value specifying
the layer into which the sprite is to be
drawn. Sprites with lower layer numbers
appear in front of sprites with higher layer
numbers. To designate a sprite as a
background sprite, you should assign it
the special layer number
kBackgroundSpriteLayerNum.

kSpritePropertyGraphicsMode 6 Specifies a graphics mode and blend color
that indicates how to blend a sprite with
any sprites behind it and with the
background. To set a sprite’s graphics
mode, you call SetSpriteProperty,
passing a pointer to a
ModifierTrackGraphicsModeRecord
structure.

kSpritePropertyActionHandlingSpriteID 8 Specifies another sprite by ID that
delegates QT events.

kSpritePropertyImageIndex 100 Contains the atom ID of the sprite’s image
atom.

The override sample differs from the key frame sample in two ways. First, the override sample does
not contain a shared data atom. All shared data must appear in the key frame. Second, only those
sprite properties that change need to be specified. If none of a sprite’s properties change in a given
frame, then the sprite does not need an atom in the differenced frame.

Sprite Media 117

C H A P T E R 3

The override sample can be used in one of two ways: combined, as with video key frames, to construct
the current frame; or the current frame can be derived by combining only the key frame and the
current override sample.

Refer to the section “Sprite Track Media Format” (page 119) for information on how override samples
are indicated in the file, using kSpriteTrackPropertySampleFormat and the default behavior of the
kKeyFrameAndSingleOverride format.

Sprite Track Properties

In addition to defining properties for individual sprites, you can also define properties that apply to
an entire sprite track. These properties may override default behavior or provide hints to the sprite
media handler. The following sprite track properties are supported:

■ The kSpriteTrackPropertyBackgroundColor property specifies a background color for the
sprite track. The background color is used for any area that is not covered by regular sprites or
background sprites. If you do not specify a background color, the sprite track uses black as the
default background color.
■ The kSpriteTrackPropertyOffscreenBitDepth property specifies a preferred bit depth for the
sprite track’s offscreen buffer. The allowable values are 8 and 16. To save memory, you should
set the value of this property to the minimum depth needed. If you do not specify a bit depth,
the sprite track allocates an offscreen buffer with the depth of the deepest intersecting monitor.
■ The kSpriteTrackPropertySampleFormat property specifies the sample format for the sprite
track. If you do not specify a sample format, the sprite track uses the default format,
kKeyFrameAndSingleOverride.

To specify sprite track properties, you create a single QT atom container and add a leaf atom for each
property you want to specify. To add the properties to a sprite track, you call the media handler
function SetMediaPropertyAtom. To retrieve a sprite track’s properties, you call the media handler
function GetMediaPropertyAtom.

The sprite track properties and their corresponding data types are listed in Table 3-6 (page 118).

Table 3-6 Sprite track properties

Atom type Atom ID Leaf data type

kSpriteTrackPropertyBackgroundColor 1 RGBColor

kSpriteTrackPropertyOffscreenBitDepth 1 unsigned short

kSpriteTrackPropertySampleFormat 1 long

kSpriteTrackPropertyHasActions 1 Boolean

kSpriteTrackPropertyQTIdleEventsFrequency 1 UInt32

kSpriteTrackPropertyVisible 1 Boolean

kSpriteTrackPropertyScaleSpritesToScaleWorld 1 Boolean

118 Sprite Track Properties

C H A P T E R 3

Note: When pasting portions of two different tracks together, the Movie Toolbox checks to see that
all sprite track properties match. If, in fact, they do match, the paste results in a single sprite track
instead of two. u

Sprite Track Media Format

The sprite track media format is hierarchical and based on QT atoms and atom containers. A sprite
track is defined by one or more key frame samples, each followed by any number of override samples.
A key frame sample and its subsequent override samples define a scene in the sprite track. A key
frame sample is a QT atom container that contains atoms defining the sprites in the scene and their
initial properties. The override samples are other QT atom containers that contain atoms that modify
sprite properties, thereby animating the sprites in the scene. In addition to defining properties for
individual sprites, you can also define properties that apply to an entire sprite track.

Figure 3-3 (page 119) shows the high-level structure of a sprite track key frame sample. Each atom in
the atom container is represented by its atom type, atom ID, and, if it is a leaf atom, the type of its
data.

Figure 3-3 A key frame sample atom container

QT atom
container

kSpriteAtomType kSpriteAtomType kSpriteSharedDataAtomType

ID:1 ID:numSprites ID:1

Sprite property atoms Shared data atoms

The QT atom container contains one child atom for each sprite in the key frame sample. Each sprite
atom has a type of kSpriteAtomType. The sprite IDs are numbered from 1 to the number of sprites
defined by the key frame sample (numSprites).

Each sprite atom contains leaf atoms that define the properties of the sprite, as shown in Figure
3-4 (page 120). For example, the kSpritePropertyLayer property defines a sprite’s layer. Each sprite
property atom has an atom type that corresponds to the property and an ID of 1.


C H A P T E R 3

Figure 3-4 Atoms that describe a sprite and its properties

kSpriteAtomType

ID:1

kSpritePropertyImageIndex kSpritePropertyLayer kSpritePropertyGraphicsMode

ID:1 ID:1 ID:1

short short ModifierTrackGraphicsModeRecord

kSpritePropertyMatrix kSpritePropertyVisible kSpriteNameAtomType kSpriteURLLinkAtomType

ID:1 ID:1 ID:1 ID:1

MatrixRecord short “The sprite name” “The URL”

In addition to the sprite atoms, the QT atom container contains one atom of type
kSpriteSharedDataAtomType with an ID of 1. The atoms contained by the shared data atom describe
data that is shared by all sprites. The shared data atom contains one atom of type
kSpriteImagesContainerAtomType with an ID of 1 ( Figure 3-5 (page 120)).

The image container atom contains one atom of type kImageAtomType for each image in the key frame
sample. The image atom IDs are numbered from 1 to the number of images (numImages). Each image
atom contains a leaf atom that holds the image data (type kSpriteImageDataAtomType) and an
optional leaf atom (type kSpriteNameAtomType) that holds the name of the image.

Figure 3-5 Atoms that describe sprite images

kSpriteSharedDataAtomType

ID:1

kSpriteImageContainerAtomType

ID:1

kSpriteImageAtomType kSpriteImageAtomType

ID:1 ID:numImages

kSpriteImageDataAtomType kSpriteNameAtomType kSpriteImageDataAtomType

ID:1 ID:1 ID:1
Image data “The image name” Image data

120 Sprite Track Media Format

C H A P T E R 3

Sprite Media Format Atoms
The sprite track’s sample format enables you to store the atoms necessary to describe action lists that
are executed in response to QuickTime events. “QT Atom Container Description Key” (page 127)
defines a grammar for constructing valid action sprite samples, which may include complex
expressions.

Both key frame samples and override samples support the sprite action atoms. Override samples
override actions at the QuickTime event level. In effect, what you do by overriding is to completely
replace one event handler and all its actions with another. The sprite track’s
kSpriteTrackPropertySampleFormat property has no effect on how actions are performed. The
behavior is similar to the default kKeyFrameAndSingleOverride format where, if in a given override
sample there is no handler for the event, the key frame’s handler is used, if there is one.

Sprite Media Format Extensions
This section describes some of the atom types and IDs used to extend the sprite track’s media format,
thus enabling action sprite capabilities.

A complete description of the grammar for sprite media handler samples, including action sprite
extensions, is included in the section “Sprite Media Handler Track Properties QT Atom Container
Format” (page 128).

Important: Some sprite track property atoms were added in QuickTime 4. In particular, you must
set the kSpriteTrackPropertyHasActions track property in order for your sprite actions to be
executed. s

Sprite Track Property Atoms
Sprite track property atoms are applied to the whole track, not just to a single sample.

Constant descriptions

kSpriteTrackPropertyHasActions
You must add an atom of this type with its leaf data set to true if you want the movie controller
to execute the actions in your sprite track’s media. The atom’s leaf data is of type Boolean. The
default value is false, so it is very important to add an atom of this type if you want
interactivity to take place.

kSpriteTrackPropertyQTIdleEventsFrequency
You must add an atom of this type if you want the sprites in your sprite track to receive
kQTEventIdle QuickTime events. The atom’s leaf data is of type UInt32. The value is the
mimimum number of ticks that must pass before the next QTIdle event is sent. Each tick is
1/60th of one second. To specify “Idle as fast as possible,” set the value to 0. The default value
is kNoQTIdleEvents, which means don’t send any idle events.

It is possible that for small idle event frequencies, the movie will not be able to keep up, in
which case idle events will be sent as fast as possible.


C H A P T E R 3

Since sending idle events takes up some time, it is best to specify the largest frequency that
produces the results that you desire, or kNoQTIdleEvents if you do not need them.

kSpriteTrackPropertyVisible
You can cause the entire sprite track to be invisible by setting the value of this Boolean property
to false. This is useful for using a sprite track as a hidden button track—for example, placing
an invisible sprite track over a video track would allow the characters in the video to be clickable.
The default value is visible (true).

kSpriteTrackPropertyScaleSpritesToScaleWorld
You can cause each sprite to be rescaled when the sprite track is resized by setting the value
of this Boolean property to true. Setting this property can improve the drawing performance
and quality of a scaled sprite track. This is particularly useful for sprite images compressed
with codecs that are resolution-independent, such as the Curve codec. The default value for
this property is false.

Atom Types

The following constants represent atom types for sprite media.

enum {
kSpriteAtomType = 'sprt',
kSpriteImagesContainerAtomType = 'imct',
kSpriteImageAtomType = 'imag',
kSpriteImageDataAtomType = 'imda',
kSpriteImageDataRefAtomType = 'imre',
kSpriteImageDataRefTypeAtomType = 'imrt',
kSpriteImageGroupIDAtomType = 'imgr',
kSpriteImageRegistrationAtomType = 'imrg',
kSpriteImageDefaultImageIndexAtomType ='defi',
kSpriteSharedDataAtomType = 'dflt',
kSpriteNameAtomType = 'name',
kSpriteImageNameAtomType = 'name',
kSpriteUsesImageIDsAtomType = 'uses',
kSpriteBehaviorsAtomType = 'beha',
kSpriteImageBehaviorAtomType = 'imag',
kSpriteCursorBehaviorAtomType = 'crsr',
kSpriteStatusStringsBehaviorAtomType = 'sstr',
kSpriteVariablesContainerAtomType = 'vars',
kSpriteStringVariableAtomType = 'strv',
kSpriteFloatingPointVariableAtomType = 'flov'
kSpriteSharedDataAtomType = 'dflt',
kSpriteURLLinkAtomType = 'url '
kSpritePropertyMatrix = 1
kSpritePropertyVisible = 4
kSpritePropertyLayer = 5
kSpritePropertyGraphicsMode = 6
kSpritePropertyImageIndex = 100
kSpritePropertyBackgroundColor = 101
kSpritePropertyOffscreenBitDepth = 102
kSpritePropertySampleFormat = 103
};

122 Atom Types

C H A P T E R 3


kSpriteAtomType
The atom is a parent atom that describes a sprite. It contains atoms that describe properties of
the sprite. Optionally, it may also include an atom of type kSpriteNameAtomType that defines
the name of the sprite.

kSpriteImagesContainerAtomType
The atom is a parent atom that contains atoms of type kSpriteImageAtomType.

kSpriteImageAtomType
The atom is a parent atom that contains an atom of type kSpriteImageDataAtomType.
Optionally, it may also include an atom of type kSpriteNameAtomType that defines the name
of the image.

kSpriteImageDataAtomType
The atom is a leaf atom that contains image data.

kSpriteSharedDataAtomType
The atom is a parent atom that contains shared sprite data, such as an atom container of type
kSpriteImagesContainerAtomType.

kSpriteNameAtomType
The atom is a leaf atom that contains the name of a sprite or an image. The leaf data is composed
of one or more ASCII characters.

kSpritePropertyImageIndex
A leaf atom containing the image index property which is of type short. This atom is a child
atom of kSpriteAtom.

kSpritePropertyLayer
A leaf atom containing the layer property which is of type short. This atom is a child atom of
kSpriteAtom.

kSpritePropertyMatrix
A leaf atom containing the matrix property which is of type MatrixRecord. This atom is a
child atom of kSpriteAtom.

kSpritePropertyVisible
A leaf atom containing the visible property which is of type short. This atom is a child atom
of kSpriteAtom.

kSpritePropertyGraphicsMode
A leaf atom containing the graphics mode property which is of type
ModifyerTrackGraphicsModeRecord. This atom is a child atom of kSpriteAtom.

kSpritePropertyBackgroundColor
A leaf atom containing the background color property which is of type RGBColor. This atom
is used in a sprite track’s MediaPropertyAtom atom container.

Atom Types 123

C H A P T E R 3

kSpritePropertyOffscreenBitDepth
A leaf atom containing the preferred offscreen bitdepth which is of type short. This atom is
used in a sprite track’s MediaPropertyAtom atom container.

kSpritePropertySampleFormat
A leaf atom containing the sample format property, which is of type short. This atom is used
in a sprite track’s MediaPropertyAtom atom container.

kSpriteImageRegistrationAtomType
Sprite images have a default registration point of 0, 0. To specify a different point, add an atom
of type kSpriteImageRegistrationAtomType as a child atom of the kSpriteImageAtomType
and set its leaf data to a FixedPoint value with the desired registration point.

kSpriteImageGroupIDAtomType
You must assign group IDs to sets of equivalent images in your key frame sample. For example,
if the sample contains ten images where the first two images are equivalent, and the last eight
images are equivalent, then you could assign a group ID of 1000 to the first two images, and
a group ID of 1001 to the last eight images. This divides the images in the sample into two sets.
The actual ID does not matter, it just needs to be a unique positive integer.

Each image in a sprite media key frame sample is assigned to a group. Add an atom of type
kSpriteImageGroupIDAtomType as a child of the kSpriteImageAtomType atom and set its
leaf data to a long containing the group ID.

Important: You must assign group IDs to your sprite sample if you want a sprite to display
images with non-equivalent image descriptions (i.e., images with different dimensions). s

For each of the following atom types (added to QuickTime 4)––except
kSpriteBehaviorsAtomType––you fill in the structure QTSpriteButtonBehaviorStruct, which
contains a value for each of the four states.

kSpriteBehaviorsAtomType
This is the parent atom of kSpriteImageBehaviorAtomType,
kSpriteCursorBehaviorAtomType, and kSpriteStatusStringsBehaviorAtomType.

kSpriteImageBehaviorAtomType
Specifies the imageIndex.

kSpriteCursorBehaviorAtomType
Specifies the cursorID.

kSpriteStatusStringsBehaviorAtomType
Specifies an ID of a string variable contained in a sprite track to display in the status area of
the browser.

124 Atom Types

C H A P T E R 3

Note: All sprite media—specifically the leaf data in the QT atom containers for sample and
sprite track properties—should be written in big-endian format. u

kSpriteUsesImageIDsAtomType
This atom allows a sprite to specify which images it uses—in other words, the subset of images
that its imageIndex propertycan refer to.

You add an atom of type kSpriteUsesImageIDsAtomType as a child of a kSpriteAtomType
atom, setting its leaf data to an array of QT atom IDs. This array contains the IDs of the images
used, not the indices.

Although QuickTime does not currently use this atom internally, tools that edit sprite media can use
the information provided to optimize certain operations, such as cut, copy, and paste.

kSpriteImageRegistrationAtomType
Sprite images have a default registration point of 0, 0. To specify a different point, you add an
atom of type kSpriteImageRegistrationAtomType as a child atom of the
kSpriteImageAtomType and set its leaf data to a FixedPoint value with the desired registration
point.

kSpriteImageGroupIDAtomType
You must assign group IDs to sets of equivalent images in your key frame sample. For example,
if the sample contains ten images where the first two images are equivalent, and the last eight
images are equivalent, then you could assign a group ID of 1000 to the first two images, and
a group ID of 1001 to the last eight images. This divides the images in the sample into two sets.
The actual ID does not matter; it just needs to be a unique positive integer.

Each image in a sprite media key frame sample is assigned to a group. You add an atom of
type kSpriteImageGroupIDAtomType as a child of the kSpriteImageAtomType atom and set
its leaf data to a long containing the group ID.

Important: You must assign group IDs to your sprite sample if you want a sprite to display
images with non-equivalent image descriptions (that is, images with different dimensions). s

You use the following atom types, which were added to QuickTime 4, to specify that an image is
referenced and how to access it.

kSpriteImageDataRefAtomType
Add this atom as a child of the kSpriteImageAtomType atom instead of a
kSpriteImageDataAtomType. Its ID should be 1. Its data should contain the data reference
(similar to the dataRef parameter of GetDataHandler).

kSpriteImageDataRefTypeAtomType
Add this atom as a child of the kSpriteImageAtomType atom. Its ID should be 1. Its data should
contain the data reference type (similar to the dataRefType parameter of GetDataHandler).

kSpriteImageDefaultImageIndexAtomType
You may optionally add this atom as a child of the kSpriteImageAtomType atom. Its ID should
be 1. Its data should contain a short, which specifies an image index of a traditional image to
use while waiting for the referenced image to load.

Atom Types 125

C H A P T E R 3

The following constants represent formats of a sprite track. The value of the constant indicates how
override samples in a sprite track should be interpreted. You set a sprite track’s format by creating a
kSpriteTrackPropertySampleFormat atom.

enum {
kKeyFrameAndSingleOverride = 1L << 1,
kKeyFrameAndAllOverrides = 1L << 2
};


kKeyFrameAndSingleOverride
The current state of the sprite track is defined by the most recent key frame sample and the
current override sample. This is the default format.

kKeyFrameAndAllOverrides
The current state of the sprite track is defined by the most recent key frame sample and all
subsequent override samples up to and including the current override sample.

Sprite Button Behaviors

In QuickTime 4, sprites in a sprite track can specify simple button behaviors. These behaviors can
control the sprite’s image, the system cursor, and the status message displayed in a Web browser.
They also provide a shortcut for a common set of actions that may result in more efficient QuickTime
movies.

Button behaviors can be added to a sprite. These behaviors are intended to make the common task
of creating buttons in a sprite track easy—you basically just fill in a template.

Three types of behaviors are available; you may choose one or more behaviors. Each change a type
of property associated with a button and are triggered by the mouse states notOverNotPressed,
overNotPressed, overPressed, and notOverPressed. The three properties changed are

■ the sprite’s imageIndex
■ the ID of a cursor to be displayed
■ the ID of a status string variable displayed in the URL status area of a Web browser.

Setting a property’s value to –1 means don’t change it.

Note: The cursor is automatically set back to the default system cursor when leaving a sprite. u

The sprite track handles letting one sprite act as an active button at a time.

The behaviors are added at the beginning of the sprite’s list of actions, so they may be overriden by
actions if desired.

To use the behaviors, you fill in the new atoms as follows, using the description key specified in “QT
Atom Container Description Key” (page 127):

126 Sprite Button Behaviors

C H A P T E R 3

kSpriteAtomType
<kSpriteBehaviorsAtomType>, 1

<kSpriteImageBehaviorAtomType>
[QTSpriteButtonBehaviorStruct]
<kSpriteCursorBehaviorAtomType>
<kSpriteStatusStringsBehaviorAtomType>

QT Atom Container Description Key

Because QT atom container–based data structures are widely used in QuickTime, a description key
is presented here. Its usage is illustrated in the following sections, “Sprite Media Handler Track
Properties QT Atom Container Format” (page 128) and “Sprite Media Handler Sample QT Atom
Container Formats” (page 128).

[(QTAtomFormatName)] =
atomType_1, id, index
data
atomType_n, id, index
data

The atoms may be required or optional:

// optional atom
// required atom
<atomType>
atomType

The atom ID may be a number if it is required to be a constant, or it may be a list of valid atom IDs,
indicating that multiple atoms of this type are allowed.

3 // one atom with id of 3
(1..3) // three atoms with id's of 1, 2, and 3
(1, 5, 7) // three atoms with id's of 1, 5, and 7
(anyUniqueIDs) // multiple atoms each with a unique id

The atom index may be a 1 if only one atom of this type is allowed, or it may be a range from 1 to
some constant or variable.

1 // one atom of this type is allowed, index is always 1
(1..3) // three atoms with indexes 1, 2, and 3
(1..numAtoms) // numAtoms atoms with indexes of 1 to numAtoms

The data may be leaf data in which its data type is listed inside of brackets [], or it may be a nested
tree of atoms.

[theDataType] // leaf data of type theDataType
childAtoms // a nested tree of atoms

Nested QTAtom format definitions [(AtomFormatName)] may appear in a definition.

QT Atom Container Description Key 127

C H A P T E R 3

Sprite Media Handler Track Properties QT Atom Container
Format

[(SpriteTrackProperties)]
<kSpriteTrackPropertyBackgroundColor, 1, 1>
[RGBColor]
<kSpriteTrackPropertyOffscreenBitDepth, 1, 1>
[short]
<kSpriteTrackPropertySampleFormat, 1, 1>
[long]
<kSpriteTrackPropertyScaleSpritesToScaleWorld, 1, 1>
[Boolean]
<kSpriteTrackPropertyHasActions, 1, 1>
[Boolean]
<kSpriteTrackPropertyVisible, 1, 1>
[Boolean]
<kSpriteTrackPropertyQTIdleEventsFrequency, 1, 1>
[UInt32]

Sprite Media Handler Sample QT Atom Container Formats

[(SpriteKeySample)] =
[(SpritePropertyAtoms)]
[(SpriteImageAtoms)]

[(SpriteOverrideSample)] =

[(SpriteImageAtoms)]
kSpriteSharedDataAtomType, 1, 1
<kSpriteVariablesContainerAtomType>, 1
<kSpriteStringVariableAtomType>, (1..n) ID is SpriteTrack
Variable ID to be set
[CString]
<kSpriteFloatingPointVariableAtomType>, (1..n) ID is
SpriteTrack Variable ID to be set
[float]

kSpriteImagesContainerAtomType, 1, 1
kSpriteImageAtomType, theImageID, (1 .. numImages)
kSpriteImageDataAtomType, 1, 1
[ImageData is ImageDescriptionHandle prepended to
image data]
<kSpriteImageRegistrationAtomType, 1, 1>
[FixedPoint]
<kSpriteImageNameAtomType, 1, 1>
[pString]
<kSpriteImageGroupIDAtomType, 1, 1>
[long]

128 Sprite Media Handler Track Properties QT Atom Container Format

C H A P T E R 3

<kQTEventFrameLoaded>, 1, 1
[(ActionListAtoms)]
<kCommentAtomType>, (anyUniqueIDs), (1..numComments)
[CString]

kSpriteAtomType, theSpriteID, (1 .. numSprites)
<kSpritePropertyMatrix, 1, 1>
[MatrixRecord]
<kSpritePropertyVisible, 1, 1>
[short]
<kSpritePropertyLayer, 1, 1>
[short]
<kSpritePropertyImageIndex, 1, 1>
[short]
<kSpritePropertyGraphicsMode, 1, 1>
[ModifierTrackGraphicsModeRecord]

<kSpriteUsesImageIDsAtomType, 1, 1>
[array of QTAtomID's, one per image used]

<kSpriteBehaviorsAtomType>, 1

<kSpriteImageBehaviorAtomType>
<kSpriteCursorBehaviorAtomType>
<kSpriteStatusStringsBehaviorAtomType>

<[(SpriteActionAtoms)]>

[(SpriteActionAtoms)] =
kQTEventType, theQTEventType, (1 .. numEventTypes)
[(ActionListAtoms)] //see the next section Wired Action
//Grammar for a description
[CString]

Wired Action Grammar

The wired action grammar shown in this section allows QT event handlers to be expressed in a
QuickTime movie. The sprite, text, VR, 3D, and Flash media handlers all support the embedding of
QT event handlers in their media samples.

[(ActionListAtoms)] =
kAction, (anyUniqueIDs), (1..numActions)
kWhichAction 1, 1
[long whichActionConstant]
<kActionParameter> (anyUniqueIDs), (1..numParameters)
[(parameterData)] ( whichActionConstant, paramIndex )
// either leaf data or child atoms
<kActionFlags> parameterID, (1..numParamsWithFlags)


C H A P T E R 3

[long actionFlags]
<kActionParameterMinValue> parameterID, (1.. numParamsWithMin)
[data depends on param type]
<kActionParameterMaxValue> parameterID, (1.. numParamsWithMax)
[data depends on param type]
[(ActionTargetAtoms)]

[CString]

[(ActionTargetAtoms)] =
<kActionTarget>
<kTargetMovie>
[no data]
kTargetChildMovieTrackName>
PString childMovieTrackNamekTargetChildMovieTrackIDlong
childMovieTrackID<kTargetChildMovieTrackIndex>
[long childMovieTrackIndex]
<kTargetChildMovieMovieName>
[PString childMovieName]
<kTargetChildMovieMovieID>
[long childMovieID]
<kTargetTrackName>
[PString trackName]
<kTargetTrackType>
[OSType trackType]
<kTargetTrackIndex>
[long trackIndex]
OR
[(kExpressionAtoms)]
<kTargetTrackID>
[long trackID]
OR
<kTargetSpriteName>
[PString spriteName]
<kTargetSpriteIndex>
[short spriteIndex]
OR
<kTargetSpriteID>
[QTAtomID spriteIID]
OR
<kTargetQD3DNamedObjectName>
[CString objectName]

[(kExpressionAtoms)] =
kExpressionContainerAtomType, 1, 1
<kOperatorAtomType, theOperatorType, 1>
kOperandAtomType, (anyUniqueIDs), (1..numOperands)
[(OperandAtoms)]
OR
<kOperandAtomType, 1, 1>
[(OperandAtoms)]
<kActionTarget>

130 Wired Action Grammar

C H A P T E R 3

<kTargetMovieName>
[Pstring MovieName]
OR
<kTargetMovieID>
[long MovieID]
OR
<
[
]
<
>
[
]

[(OperandAtoms)] =
<kOperandExpression> 1, 1
[(kExpressionAtoms)] // allows for recursion
OR
<kOperandConstant> 1, 1
[ float theConstant ]
OR
<kOperandSpriteTrackVariable> 1, 1
kActionParameter, 1, 1
[QTAtomID spriteVariableID]
OR
<kOperandKeyIsDown> 1, 1
[UInt16 modifierKeys]
[UInt8 asciiCharCode]
OR
<kOperandRandom> 1, 1
[short minimum]
[short maximum]
OR
<any other operand atom type>

The format for parameter data depends on the action and parameter index.

In most cases, the kActionParameter atom is a leaf atom containing data; for a few parameters, it
contains child atoms.

whichAction corresponds to the action type that is specified by the leaf data of a kWhichAction atom.

paramIndex is the index of the parameter’s kActionParameter atom.

[(parameterData)] ( whichAction, paramIndex ) =
{
kActionMovieSetVolume:
param1: short volume

kActionMovieSetRate


C H A P T E R 3

param1: Fixed rate

kActionMovieSetLoopingFlags
param1: long loopingFlags

kActionMovieGoToTime
param1: TimeValue time

kActionMovieGoToTimeByName
param1: Str255 timeName

kActionMovieGoToBeginning
no params

kActionMovieGoToEnd
no params

kActionMovieStepForward
no params

kActionMovieStepBackward
no params

kActionMovieSetSelection
param1: TimeValue startTime
param2: TimeValue endTime

kActionMovieSetSelectionByName
param1: Str255 startTimeName
param2: Str255 endTimeName

kActionMoviePlaySelection
param1: Boolean selectionOnly

kActionMovieSetLanguage
param1: long language

kActionMovieChanged
no params

kActionTrackSetVolume
param1: short volume

kActionTrackSetBalance
param1: short balance

kActionTrackSetEnabled
param1: Boolean enabled

kActionTrackSetMatrix
param1: MatrixRecord matrix

kActionTrackSetLayer
param1: short layer

kActionTrackSetClip
param1: RgnHandle clip


C H A P T E R 3

kActionSpriteSetMatrix
param1: MatrixRecord matrix

kActionSpriteSetImageIndex
parm1: short imageIndex

kActionSpriteSetVisible
param1: short visible

kActionSpriteSetLayer
param1: short layer

kActionSpriteSetGraphicsMode
param1: ModifierTrackGraphicsModeRecord graphicsMode

kActionSpritePassMouseToCodec
no params

kActionSpriteClickOnCodec
param1: Point localLoc

kActionSpriteTranslate
param1: Fixed x
param2: Fixed y
param3: Boolean isRelative

kActionSpriteScale
param1: Fixed xScale
param2: Fixed yScale

kActionSpriteRotate
param1: Fixed degrees

kActionSpriteStretch
param1: Fixed p1x
param2: Fixed p1y
param3: Fixed p2x
param4: Fixed p2y
param5: Fixed p3x
param6: Fixed p3y
param7: Fixed p4x
param8: Fixed p4y

kActionQTVRSetPanAngle
param1: float panAngle

kActionQTVRSetTiltAngle
param1: float tileAngle

kActionQTVRSetFieldOfView
param1: float fieldOfView

kActionQTVRShowDefaultView
no params

kActionQTVRGoToNodeID
param1: UInt32 nodeID


C H A P T E R 3

kActionMusicPlayNote
param1: long sampleDescIndex
param2: long partNumber
param3: long delay
param4: long pitch
param5: long velocity
param6: long duration

kActionMusicSetController
param1: long sampleDescIndex
param2: long partNumber
param3: long delay
param4: long controller
param5: long value

kActionCase
param1: [(CaseStatementActionAtoms)]

kActionWhile
param1: [(WhileStatementActionAtoms)]

kActionGoToURL
param1: CString urlLink

kActionSendQTEventToSprite
param1: [(SpriteTargetAtoms)]
param2: QTEventRecord theEvent

kActionDebugStr
param1: Str255 theMessageString

kActionPushCurrentTime
no params

kActionPushCurrentTimeWithLabel
param1: Str255 theLabel

kActionPopAndGotoTopTime
no params

kActionPopAndGotoLabeledTime
param1: Str255 theLabel

kActionSpriteTrackSetVariable
param1: QTAtomID variableID
param2: float value

kActionApplicationNumberAndString
param1: long aNumber
param2: Str255 aString
}

Both [(CaseStatementActionAtoms)] and [(WhileStatementActionAtoms)] are child atoms of a
kActionParameter 1, 1 atom.

[(CaseStatementActionAtoms)] =
kConditionalAtomType, (anyUniqueIDs), (1..numCases)


C H A P T E R 3

kActionListAtomType 1, 1
[(ActionListAtoms)] // may contain nested conditional actions

[(WhileStatementActionAtoms)] =
kConditionalAtomType, 1, 1
kActionListAtomType 1, 1
[(ActionListAtoms)] // may contain nested conditional actions

Flash Media

Flash is a vector-based graphics and animation technology designed for the Internet. As an authoring
tool, Flash lets content authors and developers create a wide range of interactive vector animations.
The files exported by this tool are called SWF (pronounced “swiff”) files. SWF files are commonly
played back using Macromedia’s ShockWave plug-in. In an effort to establish Flash as an industry-wide
standard, Macromedia has published the SWF File Format and made the specification publicly available
on its website at http://www.macromedia.com/software/flash/open/spec/.

The Flash media handler, introduced in QuickTime 4, allows a Macromedia Flash SWF 3.0 file to be
treated as a track within a QuickTime movie. Thus, QuickTime 4 extends the SWF file format, enabling
the execution of any of its wired actions. See “Adding Wired Actions To a Flash Track” (page 222) for
an example of how to add wired actions.

Because a QuickTime movie may contain any number of tracks, multiple SWF tracks may be added
to the same movie. The Flash media handler also provides support for an optimized case using the
alpha channel graphics mode, which allows a Flash track to be composited cleanly over other tracks.

QuickTime supports all Flash actions except for the Flash load movie action. For example, when a
Flash track in a QuickTime movie contains an action that goes to a particular Flash frame, QuickTime
converts this to a wired action that goes to the QuickTime movie time in the corresponding Flash
frame.

Note: As a time-based media playback format, QuickTime may drop frames when necessary to
maintain its schedule. As a consequence, frames of a SWF file may be dropped during playback. If
this is not satisfactory for your application, you can set the playback mode of the movie to Play All
Frames, which will emulate the playback mode of ShockWave. QuickTime’s SWF file importer sets
the Play All Frames mode automatically when adding a SWF file to an empty movie. u

QuickTime support for Flash 3.0 also includes the DoFSCommand mechanism. This allows JavaScript
routines with a specific function prototype to be invoked with parameters passed from the Flash
track. Refer to Macromedia’s Flash 3 documentation for more details on how to author a .SWF 3.0 file
with a Flash FSCommand.

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Tween Media

Tween media is used to store pairs of values to be interpolated between in QuickTime movies. These
interpolated values modify the playback of other media types by using track references and track
input maps. For example, a tween media could generate gradually changing relative volume levels
to cause an audio track to fade out. It has a media type of 'twen'.

Every tween operation is based on a collection of one or more values from which a range of output
values can be algorithmically derived. Each tween is assigned a time duration, and an output value
can be generated for any time value within the duration. In the simplest kind of tween operation, a
pair of values is provided as input and values between the two values are generated as output.

A tween track is a special track in a movie that is used exclusively as a modifier track. The data it
contains, known as tween data, is used to generate values that modify the playback of other tracks,
usually by interpolating values. The tween media handler sends these values to other media handlers;
it never presents data.

Tween Sample Description
The tween sample description uses the standard sample description header, as described in “Sample
Table Atoms” (page 70).

The data format field in the sample description is always set to 'twen'. The tween media handler

Tween Sample Data
Tween sample data is stored in QT atom structures.

At the root level, there are one or more tween entry atoms; these atoms have an atom type value of
'twen'. Each tween entry atom completely describes one interpolation operation. These atoms should
be consecutively numbered starting at 1, using the atom ID field.

Each tween entry atom contains several more atoms that describe how to perform the interpolation.
The atom ID field in each of these atoms must be set to 1.

■ Tween start atom (atom type is 'twst'). This atom specifies the time at which the interpolation
is to start. The time is expressed in the media’s time coordinate system. If this atom is not present,
the starting offset is assumed to be 0.
■ Tween duration atom (atom type is 'twdu'). This atom specifies how long the interpolation is to
last. The time is expressed in the media’s time coordinate system. If this atom is not present, the
duration is assumed to be the length of the sample.
■ Tween data atom (atom type is 'twdt'). This atom contains the actual values for the interpolation.
The contents depend on the value of the tween type atom.
■ Tween type atom (atom type is 'twnt'). Describes the type of interpolation to perform. Table
3-7 (page 137) shows all currently defined tween types. All tween types are currently supported
using linear interpolation.

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C H A P T E R 3

Table 3-7 Tween type values

Tween type Value Tween data

16-bit integer 1 Two 16-bit integers.

32-bit integer 2 Two 32-bit integers.

32-bit fixed-point 3 Two 32-bit fixed-point numbers.

Point: two 16-bit integers 4 Two points.

Rectangle: four 16-bit integers 5 Two rectangles.

QuickDraw region 6 Two rects and a region. The tween
entry atom must contain a 'qdrg'
atom with an atom ID value of 1.
The region is transformed through
the resulting matrices.

Matrix 7 Two matrices.

RGB color: three 16-bit integers 8 Two RGB colors.

Graphics mode with RGB color 9 Two graphics modes with RGB
color. Only the RGB color is
interpolated. The graphics modes
must be the same.

Each tween type is distinguished from other types by these characteristics:

■ input values or structures of a particular type
■ a particular number of input values or structures (most often one or two)
■ output values or structures of a particular type
■ a particular algorithm used to derive the output values

Tween operations for each tween type are performed by a tween component that is specific to that
type or, for a number of tween types that are native to QuickTime, by QuickTime itself. Movies and
applications that use tweening do not need to specify the tween component to use; QuickTime identifies
a tween type by its tween type identifier and automatically routes its data to the correct tween
component or to QuickTime.

When a movie contains a tween track, the tween media handler invokes the necessary component
(or built-in QuickTime code) for tween operations and delivers the results to another media handler.
The receiving media handler can then use the values it receives to modify its playback. For example,
the data in a tween track can be used to alter the volume of a sound track.

Tweening can also be used outside of movies by applications or other software that can use the values
it generates.

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C H A P T E R 3

Tween Type Categories
Each of the tween types supported by QuickTime belongs to one of these categories:

■ Numeric tween types, which have pairs of numeric values, such as long integers, as input. For
these types, linear interpolation is used to generate output values.
■ QuickDraw tween types, most of which have pairs of QuickDraw structures, such as points or
rectangle, as input. For these types, one or more structure elements are interpolated, such as the
h and v values for points, and each element that is interpolated is interpolated separately from
others.
■ 3D tween types, which have a QuickDraw 3D structure such as TQ3Matrix4x4 or
TQ3RotateAboutAxisTransformData as input. For these types, a specific 3D transformation is
performed on the data to generate output.
■ The polygon tween type, which takes three four-sided polygons as input. One polygon (such as
the bounds for a sprite or track) is transformed, and the two others specify the start and end of
the range of polygons into which the tween operation maps it. You can use the output (a
MatrixRecord data structure) to map the source polygon into any intermediate polygon. The
intermediate polygon is interpolated from the start and end polygons for each particular time in
the tween duration.
■ Path tween types have as input a QuickTime vector data stream for a path. Four of the path tween
types also have as input a percentage of path’s length; for these types, either a point on the path
or a data structure is returned. Two other path tween types treat the path as a function: one returns
the y value of the point on the path with a given x value, and the other returns the x value of the
point on the path with a given y value.
■ The list tween type has as input a QT atom container that contains leaf atoms of a specified atom
type. For this tween type category, the duration of the tween operation is divided by the number
of leaf atoms of the specified type. For time points within the first time division, the data for the
first leaf atom is returned; for the second time division, the data for the second leaf atom is
returned; and so on. The resulting tween operation proceeds in discrete steps (one step for each
leaf atom), instead of the relatively continuous tweening produced by other tween type categories.

Tween QT Atom Container
The characteristics of a tween are specified by the atoms in a tween QT atom container.

A tween QT atom container can contain the atoms described in the following sections.

General Tween Atoms

■ kTweenEntry

Specifies a tween atom, which can be either a single tween atom, a tween atom in a tween sequence,
or an interpolation tween atom.
Its parent is the tween QT atom container (which you specify with the constant
kParentAtomIsContainer).

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C H A P T E R 3

The index of a kTweenEntry atom specifies when it was added to the QT atom container; the first
added has the index 1, the second 2, and so on. The ID of a kTweenEntry atom can be any ID that
is unique among the kTweenEntry atoms contained in the same QuickTime atom container.
This atom is a parent atom. It must contain the following child atoms:
❏ A kTweenType atom that specifies the tween type.
❏ One or more kTweenData atoms that contain the data for the tween atom. Each kTweenData
atom can contain different data to be processed by the tween component, and a tween
component can process data from only one kTweenData atom a time. For example, an
application can use a list tween to animate sprites. The kTweenEntry atom for the tween atom
could contain three sets of animation data, one for moving the sprite from left to right, one
for moving the sprite from right to left, and one for moving the sprite from top to bottom. In
this case, the kTweenEntry atom for the tween atom would contain three kTweenData atoms,
one for each data set. The application specifies the desired data set by specifying the ID of
the kTweenData atom to use.
A kTweenEntry atom can contain any of the following optional child atoms:
❏ A kTweenStartOffset atom that specifies a time interval, beginning at the start of the tween
media sample, after which the tween operation begins. If this atom is not included, the tween
operation begins at the start of the tween media sample.
❏ A kTweenDuration atom that specifies the duration of the tween operation. If this atom is
not included, the duration of the tween operation is the duration of the media sample that
contains it.
If a kTweenEntry atom specifies a path tween, it can contain the following optional child
atom:
❏ A kTweenFlags atom containing flags that control the tween operation. If this atom is not
included, no flags are set.
Note that interpolation tween tracks are tween tracks that modify other tween tracks. The
output of an interpolation tween track must be a time value, and the time values generated
are used in place of the input time values of the tween track being modified.
If a kTweenEntry atom specifies an interpolation tween track, it must contain the following
child atoms:
❏ A kTweenInterpolationID atom for each kTweenData atom to be interpolated. The ID of
each kTweenInterpolationID atom must match the ID of the kTweenData atom to be
interpolated. The data for a kTweenInterpolationID atom specifies a kTweenEntry atom
that contains the interpolation tween track to use for the kTweenData atom.
If this atom specifies an interpolation tween track, it can contain either of the following
optional child atoms:
❏ A kTweenOutputMin atom that specifies the minimum output value of the interpolation tween
atom. The value of this atom is used only if there is also a kTweenOutputMax atom with the
same parent. If this atom is not included and there is a kTweenOutputMax atom with the same
parent, the tween component uses 0 as the minimum value when scaling output values of
the interpolation tween track.
❏ A kTweenOutputMax atom that specifies the maximum output value of the interpolation tween
atom. If this atom is not included, the tween component does not scale the output values of
the interpolation tween track.

■ kTweenStartOffset

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C H A P T E R 3

For a tween atom in a tween track of a QuickTime movie, specifies a time offset from the start of
the tween media sample to the start of the tween atom. The time units are the units used for the
tween track.
Its parent atom is a kTweenEntry atom.
A kTweenEntry atom can contain only one kTweenStartOffset atom. The ID of this atom is
always 1. The index of this atom is always 1.
This atom is a leaf atom. The data type of its data is TimeValue.
This atom is optional. If it is not included, the tween operation begins at the start of the tween
media sample.
■ kTweenDuration

Specifies the duration of a tween operation. When a QuickTime movie includes a tween track,
the time units for the duration are those of the tween track. If a tween component is used outside
of a movie, the application using the tween data determines how the duration value and values
returned by the component are interpreted.
A kTweenEntry atom can contain only one kTweenDuration atom. The ID of this atom is always
1. The index of this atom is always 1.
This atom is a leaf atom. The data type of its data is TimeValue.
This atom is optional. If it is not included, the duration of the tween operation is the duration of
the media sample that contains it.
■ kTweenData

Contains data for a tween atom.
A kTweenEntry atom can contain any number of kTweenData atoms.
The index of a kTweenData atom specifies when it was added to the kTweenEntry atom; the first
added has the index 1, the second 2, and so on. The ID of a kTweenData atom can be any ID that
is unique among the kTweenData atoms contained in the same kTweenEntry atom.
At least one kTweenData atom is required in a kTweenEntry atom.
For single tween atoms, a kTweenData atom is a leaf atom. It can contain data of any type.
For polygon tween atoms, a kTweenData atom is a leaf atom. The data type of its data is Fixed[27],
which specifies three polygons.
For path tweens, a kTweenData atom is a leaf atom. The data type of its data is Handle, which
contains a QuickTime vector.
In interpolation tween atoms, a kTweenData atom is a leaf atom. It can contain data of any type.
An interpolation tween atom can be any tween atoms other than a list tween atom that returns a
time value.
In list tween atoms, a kTweenData atom is a parent atom that must contain the following child
atoms:
❏ A kListElementType atom that specifies the atom type of the elements of the tween atom.
❏ One or more leaf atoms of the type specified by the kListElementType atom. The data for
each atom is the result of a list tween operation.

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■ kNameAtom

Specifies the name of a tween atom. The name, which is optional, is not used by tween components,
but it can be used by applications or other software.
A kTweenEntry atom can contain only one kNameAtom atom. The ID of this atom is always 1. The
index of this atom is always 1.
This atom is a leaf atom. Its data type is String.
This atom is optional. If it is not included, the tween atom does not have a name.
■ kTweenType

Specifies the tween type (the data type of the data for the tween operation).
A kTweenEntry atom can contain only one kTweenType atom. The ID of this atom is always 1.
The index of this atom is always 1.
This atom is a leaf atom. The data type of its data is OSType.
This atom is required.

Path Tween Atoms

■ kTweenFlags

Contains flags that control the tween operation. One flag that controls path tween atoms is defined:
❏ The kTweenReturnDelta flag applies only to path tween atoms (tweens of type
kTweenTypePathToFixedPoint, kTweenTypePathToMatrixTranslation,
kTweenTypePathToMatrixTranslationAndRotation, kTweenTypePathXtoY, or
kTweenTypePathYtoX). If the flag is set, the tween component returns the change in value
from the last time it was invoked. If the flag is not set, or if the tween component has not
previously been invoked, the tween component returns the normal result for the tween atom.
A kTweenEntry atom can contain only one kTweenFlags atom. The ID of this atom is always
This atom is a leaf atom. The data type of its data is Long.
This atom is optional. If it is not included, no flags are set.

■ kInitialRotationAtom

Specifies an initial angle of rotation for a path tween atom of type
kTweenTypePathToMatrixRotation, kTweenTypePathToMatrixTranslation, or
kTweenTypePathToMatrixTranslationAndRotation.

A kTweenEntry atom can contain only one kInitialRotationAtom atom. The ID of this atom is
always 1. The index of this atom is always 1.
This atom is a leaf atom. Its data type is Fixed.
This atom is optional. If it is not included, no initial rotation of the tween atom is performed.

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C H A P T E R 3

List Tween Atoms

■ kListElementType

Specifies the atom type of the elements in a list tween atom.
Its parent atom is a kTweenData atom.
A kTweenEntry atom can contain only one kListElementType atom. The ID of this atom is always
This atom is a leaf atom. Its data type is QTAtomType.
This atom is required in the kTweenData atom for a list tween atom.

3D Tween Atoms

■ kTween3dInitialCondition

Specifies an initial transform for a 3D tween atom whose tween type is one of the following:
kTweenType3dCameraData, kTweenType3dMatrix, kTweenType3dQuaternion,
kTweenType3dRotate, kTweenType3dRotateAboutAxis, kTweenType3dRotateAboutAxis,
kTweenType3dRotateAboutPoint, kTweenType3dRotateAboutVector, kTweenType3dScale,
or kTweenType3dTranslate.
A kTweenEntry atom can contain only one kTween3dInitialCondition atom. The ID of this
atom is always 1. The index of this atom is always 1.
This atom is a leaf atom. The data type of its data is as follows:
❏ For a kTweenType3dCameraData tween, its data type is TQ3CameraData.
❏ For a kTweenType3dMatrix tween, its data type is TQ3Matrix4x4.
❏ For a kTweenType3dQuaternion tween, its data type is TQ3Quaternion.
❏ For a kTweenType3dRotate tween, its data type is TQ3RotateTransformData.
❏ For a kTweenType3dRotateAboutAxis tween, its data type is
TQ3RotateAboutAxisTransformData.

❏ For a kTweenType3dRotateAboutPoint tween, its data type is
TQ3RotateAboutPointTransformData.

❏ For a kTweenType3dRotateAboutVector tween, its data type is TQ3PlaneEquation.
❏ For a kTweenType3dScale tween, its data type is TQ3Vector3D.
❏ For a kTweenType3dTranslate tween, its data type is TQ3Vector3D.
This atom is optional. For each tween type, the default value is the data structure that specifies
an identity transform, that is, a transform that does not alter the 3D data.

Interpolation Tween Atoms

■ kTweenOutputMax

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C H A P T E R 3

Specifies the maximum output value of an interpolation tween atom. If a kTweenOutputMax atom
is included for an interpolation tween, output values for the tween atom are scaled to be within
the minimum and maximum values. The minimum value is either the value of the
kTweenOutputMin atom or, if there is no kTweenOutputMin atom, 0. For example, if an interpolation
tween atom has values between 0 and 4, and it has kTweenOutputMin and kTweenOutputMax
atoms with values 1 and 2, respectively, a value of 0 (the minimum value before scaling) is scaled
to 1 (the minimum specified by the kTweenOutputMin atom), a value of 4 (the maximum value
before scaling) is scaled to 2 (the maximum specified by the kTweenOutputMax atom), and a value
of 3 (three-quarters of the way between the maximum and minimum values before scaling) is
scaled to 1.75 (three-quarters of the way between the values of the kTweenOutputMin and
kTweenOutputMax atoms).

A kTweenEntry atom can contain only one kTweenOutputMax atom. The ID of this atom is always
This atom is a leaf atom. The data type of its data is Fixed.
This atom is optional. If it is not included, QuickTime does not scale interpolation tween values.
■ kTweenOutputMin

Specifies the minimum output value of an interpolation tween atom. If both kTweenOutputMin
and kTweenOutputMax atoms are included for an interpolation tween atom, output values for the
tween atom are scaled to be within the minimum and maximum values. For example, if an
interpolation tween atom has values between 0 and 4, and it has kTweenOutputMin and
kTweenOutputMax atoms with values 1 and 2, respectively, a value of 0 (the minimum value
before scaling) is scaled to 1 (the minimum specified by the kTweenOutputMin atom), a value of
4 (the maximum value before scaling) is scaled to 2 (the maximum specified by the
kTweenOutputMax atom), and a value of 3 (three-quarters of the way between the maximum and
minimum values before scaling) is scaled to 1.75 (three-quarters of the way between the values
of the kTweenOutputMin and kTweenOutputMax atoms).
If a kTweenOutputMin atom is included but a kTweenOutputMax atom is not, QuickTime does not
scale interpolation tween values.
A kTweenEntry atom can contain only one kTweenOutputMin atom. The ID of this atom is always
This atom is a leaf atom. The data type of its data is Fixed.
This atom is optional. If it is not included but a kTweenOutputMax atom is, the tween component
uses 0 as the minimum value for scaling values of an interpolation tween atom.
■ kTweenInterpolationID

Specifies an interpolation tween atom to use for a specified kTweenData atom. There can be any
number of kTweenInterpolationID atoms for a tween atom, one for each kTweenData atom to
be interpolated.
The index of a kTweenInterpolationID atom specifies when it was added to the kTweenEntry
atom; the first added has the index 1, the second 2, and so on. The ID of a kTweenInterpolationID
atom must match the atom ID of the kTweenData atom to be interpolated, and be unique among
the kTweenInterpolationID atoms contained in the same kTweenEntry atom.
This atom is a leaf atom. The data type of its data is QTAtomID.

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C H A P T E R 3

This atom is required for an interpolation tween atom.

Region Tween Atoms

■ kTweenPictureData

Contains the data for a QuickDraw picture. Used only by a kTweenTypeQDRegion atom.
A kTweenEntry atom can contain only one kTweenPictureData or kTweenRegionData atom.
The ID of this atom is always 1. The index of this atom is always 1.
This atom is a leaf atom. The data type of its data is Picture.
Either a kTweenPictureData or kTweenRegionData atom is required for a kTweenTypeQDRegion
atom.
■ kTweenRegionData

Contains the data for a QuickDraw region. Used only by a kTweenTypeQDRegion atom.
A kTweenEntry atom can contain only one kTweenRegionData or kTweenPictureData atom.
The ID of this atom is always 1. The index of this atom is always 1.
This atom is a leaf atom. The data type of its data is Region.
Either a kTweenPictureData or kTweenRegionData atom is required for a kTweenTypeQDRegion
tween.

Sequence Tween Atoms

■ kTweenSequenceElement

Specifies an entry in a tween sequence.
Its parent is the tween QT atom container (which you specify with the constant
kParentAtomIsContainer).

The ID of a kTweenSequenceElement atom must be unique among the kTweenSequenceElement
atoms in the same QT atom container. The index of a kTweenSequenceElement atom specifies its
order in the sequence; the first entry in the sequence has the index 1, the second 2, and so on.
This atom is a leaf atom. The data type of its data is TweenSequenceEntryRecord, a data structure
that contains the following fields:

endPercent
A value of type Fixed that specifies the point in the duration of the tween media sample at
which the sequence entry ends. This is expressed as a percentage; for example, if the value is
75.0, the sequence entry ends after three-quarters of the total duration of the tween media
sample have elapsed. The sequence entry begins after the end of the previous sequence entry
or, for the first entry in the sequence, at the beginning of the tween media sample.

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tweenAtomID
A value of type QTAtomID that specifies the kTweenEntry atom containing the tween for the
sequence element. The kTweenEntry atom and the kTweenSequenceElement atom must both
be a child atoms of the same tween QT atom container.

dataAtomID
A value of type QTAtomID that specifies the kTweenData atom containing the data for the tween.
This atom must be a child atom of the atom specified by the tweenAtomID field.

Modifier Tracks

The addition of modifier tracks in QuickTime 2.1 introduced the capability for creating dynamic
movies. (A modifier track sends data to another track; by comparision, a track reference is an
association.) For example, instead of playing video in a normal way, a video track could send its
image data to a sprite track. The sprite track then could use that video data to replace the image of
one of its sprites. When the movie is played, the video track appears as a sprite.

Modifier tracks are not a new type of track. Instead, they are a new way of using the data in existing
tracks. A modifier track does not present its data, but sends it to another track that uses the data to
modify how it presents its own data. Any track can be either a sender or a presenter, but not both.
Previously, all tracks were presenters.

Another use of modifier tracks is to store a series of sound volume levels, which is what occurs when
you work with a tween track. These sound levels can be sent to a sound track as it plays to dynamically
adjust the volume. A similar use of modifier tracks is to store location and size information. This data
can be sent to a video track to cause it to move and resize as it plays.

Because a modifier track can send its data to more than one track, you can easily synchronize actions
between multiple tracks. For example, a single modifier track containing matrices as its samples can
make two separate video tracks follow the same path.

See “Creating Movies With Modifier Tracks” (page 220) for more information about using modifier
tracks.

Limitations of Spatial Modifier Tracks
A modifier track may cause a track to move outside of its original boundary regions. This may present
problems, since applications do not expect the dimensions or location of a QuickTime movie to change
over time.

To ensure that a movie maintains a constant location and size, the Movie Toolbox limits the area in
which a spatially modified track can be displayed. A movie’s “natural” shape is defined by the region
returned by the GetMovieBoundsRgn function. The toolbox clips all spatially modified tracks against
the region returned by GetMovieBoundsRgn. This means that a track can move outside of its initial
boundary regions, but it cannot move beyond the combined initial boundary regions of all tracks in
the movie. Areas uncovered by a moving track are handled by the toolbox in the same way as areas
uncovered by tracks with empty edits.

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If a track has to move through a larger area than that defined by the movie’s boundary region, the
movie’s boundary region can be enlarged to any desired size by creating a spatial track (such as a
video track) of the desired size but with no data. As long as the track is enabled, it contributes to the
boundary regions of the movie.

Track References

Although QuickTime has always allowed the creation of movies that contain more than one track, it
has not been able to specify relationships between those tracks. Track references are a feature of
QuickTime that allows you to relate a movie’s tracks to one another. The QuickTime track-reference
mechanism supports many-to-many relationships. That is, any movie track may contain one or more
track references, and any track may be related to one or more other tracks in the movie.

Track references can be useful in a variety of ways. For example, track references can be used to relate
timecode tracks to other movie tracks. You can use track references to identify relationships between
video and sound tracks—identifying the track that contains dialog and the track that contains
background sounds, for example. Another use of track references is to associate one or more text
tracks that contain subtitles with the appropriate audio track or tracks.

Track references are also used to create chapter lists, as described in the next section.

Every movie track contains a list of its track references. Each track reference identifies another related
track. That related track is identified by its track identifier. The track reference itself contains
information that allows you to classify the references by type. This type information is stored in an
OSType data type. You are free to specify any type value you want. Note, however, that Apple has
reserved all lowercase type values.

You may create as many track references as you want, and you may create more than one reference
of a given type. Each track reference of a given type is assigned an index value. The index values start
at 1 for each different reference type. The Movie Toolbox maintains these index values, so that they
always start at 1 and count by 1.

Using the AddTrackReference function, you can relate one track to another. The
DeleteTrackReference function will remove that relationship. The SetTrackReference and
GetTrackReference functions allow you to modify an existing track reference so that it identifies a
different track. The GetNextTrackReferenceType and GetTrackReferenceCount functions allow
you to scan all of a track’s track references.

Chapter Lists

A chapter list provides a set of named entry points into a movie, allowing the user to jump to a
preselected point in the movie from a convenient pop-up list.

The movie controller automatically recognizes a chapter list and will create a pop-up list from it.
When the user makes a selection from the pop-up, the controller will jump to the appropriate point
in the movie. Note that if the movie is sized so that the controller is too narrow to display the chapter
names, the pop-up list will not appear.

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To create a chapter list, you must create a text track with one sample for each chapter. The display
time for each sample corresponds to the point in the movie that marks the beginning of that chapter.
You must also create a track reference of type 'chap' from an enabled track of the movie to the text
track. It is the 'chap' track reference that makes the text track into a chapter list. The track containing
the reference can be of any type (audio, video, MPEG, and so on), but it must be enabled for the
chapter list to be recognized.

Given an enabled track myVideoTrack, for example, you can use the AddTrackReference function
to create the chapter reference:

AddTrackReference( myVideoTrack, theTextTrack,
kTrackReferenceChapterList,
&addedIndex );

kTrackReferenceChapterList is defined in Movies.h. It has the value 'chap'.

The text track that constitutes the chapter list does not need to be enabled, and normally is not. If it
is enabled, the text track will be displayed as part of the movie, just like any other text track, in addition
to functioning as a chapter list.

If more than one enabled track includes a 'chap' track reference, QuickTime uses the first chapter
list that it finds.

3D Media

QuickTime movies store 3D image data in a base media. This media has a media type of 'qd3d'.

3D Sample Description
The 3D sample description uses the standard sample description header, as described in “Sample
Table Atoms” (page 70).

The data format field in the sample description is always set to 'qd3d'. The 3D media handler adds
no additional fields to the sample description.

3D Sample Data
The 3D samples are stored in the 3D Metafile format developed for QuickDraw 3D.

Streaming Media

QuickTime movies store streaming data in a streaming media track. This media has a media type of
'strm'.

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Streaming Media Sample Description
The streaming media sample description contains information that defines how to interpret streaming
media data. This sample description is based on the standard sample description header, as described
in “Sample Table Atoms” (page 70).

The streaming media sample description is documented in the QuickTime header file QTSMovie.h,
as shown in Listing 3-1 (page 148).

Listing 3-1 Streaming media sample description

struct QTSSampleDescription {
long descSize;
long dataFormat;
long resvd1; /* set to 0*/
short resvd2; /* set to 0*/
short dataRefIndex;
UInt32 version;
UInt32 resvd3; /* set to 0*/
SInt32 flags;
/* qt atoms follow:*/
/* long size, long type, some data*/
/* repeat as necessary*/
};
typedef struct QTSSampleDescription QTSSampleDescription;

The sample format depends on the dataFormat field of the QTSSampleDescription. The dataFormat
field can be any value you specify. The currently defined values are 'rtsp' and 'sdp '.

If 'rtsp', the sample can be just an rtsp URL. It can also be any value that you can put in a .rtsp
file, as defined at

http://streaming.apple.com/qtstreaming/documentation/userdocs/rtsptags.htm

If 'sdp ', then the sample is an SDP file. This would be used to receive a multicast broadcast.

Hint Media

The QuickTime file format supports streaming of media data over a network as well as local playback.
The process of sending protocol data units is time-based, just like the display of time-based data, and
is therefore suitably described by a time-based format. A QuickTime file or movie that supports
streaming includes information about the data units to stream. This information is included in
additional tracks of the movie called hint tracks.

Hint tracks contain instructions for a streaming server which assist in the formation of packets. These
instructions may contain immediate data for the server to send (for example, header information) or
reference segments of the media data. These instructions are encoded in the QuickTime file in the
same way that editing or presentation information is encoded in a QuickTime file for local playback.

Instead of editing or presentation information, information is provided which allows a server to
packetize the media data in a manner suitable for streaming, using a specific network transport.

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C H A P T E R 3

The same media data is used in a QuickTime file which contains hints, whether it is for local playback,
or streaming over a number of different transport types. Separate hint tracks for different transport
types may be included within the same file and the media will play over all such transport types
without making any additional copies of the media itself. In addition, existing media can be easily
made streamable by the addition of appropriate hint tracks for specific transports. The media data
itself need not be recast or reformatted in any way.

Typically, hinting is performed by media packetizer components. QuickTime selects an appropriate
media packetizer for each track and routes each packetizer's output through an Apple-provided
packet builder to create a hint track. One hint track is created for each streamable track in the movie.

Hint tracks are quite small compared with audio or video tracks. A movie that contains hint tracks
can be played from a local disk or streamed over HTTP, similar to any other QuickTime movie. Hint
tracks are only used when streaming a movie over a real-time media streaming protocol, such as RTP.

Support for streaming in the QuickTime file format is based upon the following considerations:

■ Media data represented as a set of network-independent standard QuickTime tracks, which may
be played or edited, as normal.
■ A common declaration and base structure for server hint tracks; this common format is protocol
independent, but contains the declarations of which protocols are described in the server tracks.
■ A specific design of the server hint tracks for each protocol which may be transmitted; all these
designs use the same basic structure.

The resulting streams, sent by the servers under the direction of hint tracks, do not need to contain
any trace of QuickTime information. This approach does not require that QuickTime, or its structures
or declaration style, be used either in the data on the wire or in the decoding station. For example, a
QuickTime file using H.261 video and DVI audio, streamed under Real-Time Protocol (RTP), results
in a packet stream which is fully compliant with the IETF specifications for packing those codings
into RTP.

Hint tracks are built and flagged, so that when the movie is viewed directly (not streamed), they are
ignored.

The next section describes a generic format for streaming hints to be stored in a QuickTime movie.

Adding Hint Tracks to a Movie
To store packetization hints, one or more hint tracks are added to a movie. Each hint track contains
hints for at least one actual media track to be streamed. A streamed media track may have more than
one hint track. For example, it might have a separate hint track for the different packet sizes the server
supports, or it might have different hint tracks for different protocols. It is not required that all media
tracks have corresponding hint tracks in a movie.

The sample time of a hint sample corresponds to the sample time of the media contained in the packets
generated by that hint sample. The hint sample may also contain a transmission time for each packet.
(The format for the hint sample is specific to the hint track type.)

The hint track may have a different time scale than its referenced media tracks.

The flags field in the track header atom ('tkhd') must be set to 0x000000, indicating that the track
is inactive and is not part of the movie, preview, or poster.

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The subType field of the handler description atom ('hdlr') contains 'hint', indicating that the media
type is packetization hints.

Note that if a QuickTime media track is edited, any previously stored packetization hints may become
invalid. Comparing the modification dates of the media track and the hint track is one way to determine
this scenario, but is far from being foolproof. Since the hint track keeps track of which original track
media samples and sample descriptions to play at specific times, changes that affect those parts of
the original track or media make those hints invalid. Changes to a movie that do not invalidate existing
hint tracks include flattening (when there are no edit lists), and adding new tracks. Changes that
invalidate hint tracks include

■ flattening (when there are edit lists)
■ adding or deleting samples
■ changing a track’s time scale
■ changing sample descriptions

Warning: Hint tracks are marked as inactive, so calling the FlattenMovie function with the
flattenActiveTracksOnly bit set deletes all hint tracks from a movie. s

Packetization Hint Media Header Atom
In QuickTime movies, the media information atom ('minf') contains header data specific to the
media. For hint tracks, the media header is a base media information atom ('gmhd'). The hint track
must contain the base media information atom.

Hint Track User Data Atom
Each hint track may contain track user data atoms that apply to only to the corresponding hint track.
There are currently two such atoms defined.

■ User data atom type 'hinf'.

This contains statistics for the hint track. The 'hinf' atom contains child atoms as defined in Table
3-8 (page 151). In some cases, there are both 32-bit and 64-bit counters available. Any unknown types
should be ignored.

■ User data atom type 'hnti'.

This may contain child atoms. Child atoms that start with 'sdp ' (note, again, the space) contain SDP
text for this track. Text from these child atoms must be inserted into the proper place in the SDP text
for the movie, after any common SDP text. This is analagous to the movie-level 'hnti' atom.

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Movie Hint Info Atom
A movie may contain a 'hnti' movie user data atom, which may contain one or more child atoms.
The child atom contents start with 4 bytes that specify the transport and 4 bytes that specify the type
of data contined in the rest of the child atom. Currently, the only defined transport is 'rtp ' (note
the space) and the only content data type defined is 'sdp ' (note the space). Child atoms whose
transport or type combinations you don’t recognize should be skipped.

The text in an atom of type 'rtp sdp ' should be inserted (in the proper place) into the SDP
information generated from this file (for example, by a streaming server) before any SDP information
for specific tracks.

Table 3-8 The 'hinf'atom type containing child atoms

Type Value Description

'trpy' 8 bytes The total number of bytes that will be sent, including
12-byte RTP headers, but not including any network
headers.

'totl' 4 bytes 4-byte version of ‘trpy’

'nump' 8 bytes The total number of network packets that will be sent
(if the application knows there is a 28-byte network
header, it can multiply 28 by this number and add it
to the ‘trpy’ value to get the true number of bytes
sent.

'npck' 4 bytes 4-byte version of ‘nump’

'tpyl' 8 bytes The total number of bytes that will be sent, not
including 12-byte RTP headers.

'tpay' 4 bytes 4-byte version of ‘tpyl’

'maxr' 8 bytes The maximum data rate. This atom contains two
numbers: g, followed by m (both 32-bit values). g is
the granularity, in milliseconds. m is the maximum
data rate given that granularity. For example, if g is 1
second, then m is the maximum data rate over any 1
second. There may be multiple 'maxr' atoms, with
different values for g. The maximum data rate
calculation does not include any network headers (but
does include 12-byte RTP headers).

'dmed' 8 bytes The number of bytes from the media track to be sent.

'dimm' 8 bytes The number of bytes of immediate data to be sent.

'drep' 8 bytes The number of bytes of repeated data to be sent.

'tmin' 4 bytes The smallest relative transmission time, in
milliseconds.

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Type Value Description

'tmax' 4 bytes The largest relative transmission time, in milliseconds.

'pmax' 4 bytes The largest packet, in bytes; includes 12-byte RTP
header.

'dmax' 4 bytes The largest packet duration, in milliseconds.

'payt' variable The payload type, which includes payload number
(32-bits) followed by rtpmap payload string (Pascal
string).

Note: Any of the atoms shown in Table 3-8 (page 151) may or may not be present. These atoms are
not guaranteed.

Finding an Original Media Track From a Hint Track

Like any other QuickTime track, hint tracks can contain track reference atoms. Exactly one of these
must be of track reference type 'hint', and its internal list must contain at least one track ID, which
is the track ID of the original media track. Like other track reference atoms, there may be empty
references in this list, indicated by a track ID of 0. For hint tracks that refer to more than one track,
the index number (starting at 1, and including any 0 entries) is used in the media track reference index
field in some of the packet data table entry modes.

For example, if you have MPEG-1 video at track ID 11 and MPEG-1 layer 2 audio at track ID 12, and
you are creating a RTP hint track that encapsulates these in an MPEG-2 transport, you need to refer
to both tracks. You can also assume that there are some empty entries and other track references in
your hint track atom reference atom’s list. So it might look like this: 11, 0, 0, 14, 0, 12, 0. When you
are assembling packets from audio and video tracks 11 and 12, you use their list indexes (1 and 6) in
the media track ref index field.

If you have only one media track listed in your hint track reference, you may simply use a 0 in the
media track ref index field.

RTP Hint Tracks

RTP hint tracks contain information that allows a streaming server to create RTP streams from a
QuickTime movie, without requiring the server to know anything about the media type, compression,
or payload format.

In RTP, each media stream, such as an audio or video track, is sent as a separate RTP stream.
Consequently, each media track in the movie has an associated RTP hint track containing the data
necessary to packetize it for RTP transport, and each hint track contains a track reference back to its
associated media track.

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Media tracks that do not have an associated RTP hint track cannot be streamed over RTP, and should
be ignored by RTP streaming servers.

It is possible for a media track to have more than one associated hint track. The hint track contains
information such as the packet size and time scale in the hint track’s sample description. This minimizes
the runtime server load, but in order to support multiple packet sizes, it is necessary to have multiple
RTP hint tracks for each media track, each with different a packet size. A similar mechanism could
be used to provide hint tracks for multiple protocols in the future.

It is also possible for a single hint track to refer to more than one media stream. For example, audio
and video MPEG elementary streams could be multiplexed into a single systems stream RTP payload
format, and a single hint track would contain the necessary information to combine both elementary
streams into a single series of RTP packets.

This is the exception rather than the rule, however. In general, multiplexing is achieved by using IP’s
port-level multiplexing, not by interleaving the data from multiple streams into a single RTP session.

The hint track is related to each base media track by a track reference declaration. The sample
description for RTP declares the maximum packet size which this hint track will generate. Partial
session description (SDP) information is stored in the track’s user data atom.

Hint Sample Data Format

The sample description atom ('stsd') contains information about the hint track samples. It specifies
the data format (note that currently only RTP data format is defined) and which data reference to use
(if more than one is defined) to locate the hint track sample data. It also contains some general
information about this hint track, such as the hint track version number, the maximum packet size
allowed by this hint track, and the RTP time scale. It may contain additional information, such as the
random offsets to add to the RTP time stamp and sequence number.

The sample description atom can contain a table of sample descriptions to accommodate media that
are encoded in multiple formats, but a hint track can be expected to have a single sample description
at this time.

The sample description for hint tracks is defined in Table 3-9.

Table 3-9 Hint track sample description

Field Bytes

Size 4

Data format 4

Reserved 6

Data reference index 2

Hint track version 2

Last compatible hint track 2
version

Hint Sample Data Format 153

C H A P T E R 3

Field Bytes

Max packet size 4

Additional data table variable

Field descriptions

Size
A 32-bit integer specifying the size of this sample description in bytes.

Data format
A four-character code indicating the data format of the hint track samples. Only 'rtp ' is
currently defined. Note that the fourth character in 'rtp ' is an ASCII blank space (hex 20).
Do not attempt to packetize data whose format you do not recognize.

Reserved
Six bytes that must be set to 0.

Data reference index
This field indirectly specifies where to find the hint track sample data. The data reference is a
file or resource specified by the data reference atom ('dref') inside the data information atom
('dinf') of the hint track. The data information atom can contain a table of data references,
and the data reference index is a 16-bit integer that tells you which entry in that table should
be used. Normally, the hint track has a single data reference, and this index entry is set to 0.

Hint track version
A 16-bit unsigned integer indicating the version of the hint track specification. This is currently
set to 1.

Hint track version

Last compatible hint track version
A 16-bit unsigned integer indicating the oldest hint track version with which this hint track is
backward-compatible. If your application understands the hint track version specified by this
field, it can work with this hint track.

Max packet size
A 32-bit integer indicating the packet size limit, in bytes, used when creating this hint track.
The largest packet generated by this hint track will be no larger than this limit.

Additional data table
A table of variable length containing additional information. Additional information is formatted
as a series of tagged entries.

This field always contains a tagged entry indicating the RTP time scale for RTP data. All other
tagged entries are optional.

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Three data tags are currently defined for RTP data. One tag is defined for use with any type
of data. You can create additional tags. Tags are identified using four-character codes. Tags
using all lowercase letters are reserved by Apple. Ignore any tagged data you do not understand.

Table entries are structured like atoms. The structure of table entries is shown in Table
3-10 (page 155).

Table 3-10 The structure of table entries

Field Format Bytes

Entry length 32-bit integer 4

Data tag 4-char code 4

Data Variable Entry length - 8

Tagged entries for the 'rtp ' data format are defined as follows:

'tims'
A 32-bit integer specifying the RTP time scale. This entry is required for RTP data.

'tsro'
A 32-bit integer specifying the offset to add to the stored time stamp when sending RTP packets.
If this entry is not present, a random offset should be used, as specified by the IETF. If this
entry is 0, use an offset of 0 (no offset).

'snro'
A 32-bit integer specifying the offset to add to the sequence number when sending RTP packets.
If this entry is not present, a random offset should be used, as specified by the IETF. If this
entry is 0, use an offset of 0 (no offset).

Packetization Hint Sample Data for Data Format 'rtp '

This section describes the sample data for the 'rtp ' format. The 'rtp ' format assumes that the
server is sending data using Real-Time Transport Protocol (RTP). This format also assumes that the
server “knows” about RTP headers but does not require that the server know anything about specific
media headers, including media headers defined in various IETF drafts.

Each sample in the hint track will generate one or more RTP packets. Each entry in the sample data
table in a hint track sample corresponds to a single RTP packet. Samples in the hint track may or may
not correspond exactly to samples in the media track. Data in the hint track sample is byte aligned,
but not 32-bit aligned.

The RTP timestamps of all packets in a hint sample are the same as the hint sample time. In other
words, packets that do not have the same RTP timestamp cannot be placed in the same hint sample.

The RTP hint track time scale should be reasonably chosen so that there is adequate spacing between
samples (as well as adequate spacing between transmission times for packets within a sample).


C H A P T E R 3

The packetization hint sample data contains the following data elements.

Packetization hint sample data Bytes

Entry count 2

Reserved 2

Packet entry table variable

Additional data variable

Field descriptions

Entry count
A 16-bit unsigned integer indicating the number of packet entries in the table. Each entry in
the table corresponds to a packet. Multiple entries in a single sample indicate that the media
sample had to be split into multiple packets. A sample with an entry count of 0 is reserved
and, if encountered, must be skipped.

Reserved
Two bytes that must be set to 0.

Packet entry table
A variable length table containing packet entries. Packet entries are defined below.

Additional data
A variable length field containing data pointed to by the entries in the data table.

The packet entry contains the following data elements.

Packet entry Bytes

Relative packet transmission time 4

RTP header info 2

RTP sequence number 2

Flags 2

Entry count 2

Extra information TLVs 0 or variable

Data table variable

Relative packet transmission time
A 32-bit signed integer value, indicating the time, in the hint track’s time scale, to send this
packet relative to the hint sample’s actual time. Negative values mean that the packet will be
sent earlier than real time, which is useful for smoothing the data rate. Positive values are

156 Packetization Hint Sample Data for Data Format 'rtp '

C H A P T E R 3

useful for repeating packets at later times. Within each hint sample track, each packet time
stamp must be non-decreasing.

RTP header info
A 16-bit integer specifying various values to be set in the RTP header. The bits of the field are
defined as follows.
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
reserved P X reserved M payload type

The RTP header information field contains the following elements.

Field Bit# Description

P 2 A 1-bit number corresponding to the padding (P) bit in the
RTP header. This bit should probably not be set, since a
server that needs different packet padding would need to
un-pad and re-pad the packet itself.

X 3 A 1-bit number corresponding to the extension (X) bit in
the RTP header. This bit should probably not be set, since
a server that needs to send its own RTP extension would
either not be able to, or would be forced to replace any
extensions from the hint track.

M 8 A 1-bit number corresponding to the marker (M) bit in the
RTP header.

Payload type 9-15 A 7-bit number corresponding to the payload type (PT)
field of the RTP header.

All undefined bits are reserved and must be set to zero. Note that the location of the defined bits are
in the same bit location as in the RTP header.

RTP sequence number
A 16-bit integer specifying the RTP sequence number for this packet. The RTP server adds a
random offset to this sequence number before transmitting the packet. This field allows
re-transmission of packets––for example, the same packet can be assembled with the same
sequence number and a different (later) packet transmission time. A text sample with a duration
of 5 minutes can be retransmitted every 10 seconds, so that clients that miss the original sample
transmission (perhaps they started playing the movie in the middle) will be refreshed after a
maximum of 10 seconds.

Flags
A 16-bit field indicating certain attributes for this packet. Defined bits are:

0 1 12 13 14 15
reserved X B R

The RTP header information field contains the following elements.


C H A P T E R 3

Field Bit# Description

X 13 A 1-bit number indicating that this packet contains an Extra
information TLV data table.

B 14 A 1-bit number indicating that this packet contains data that is
part of a b-frame. A server that is having difficulty being able to
send all the packets in real time may discard packets that have
this bit set, until it catches up with the clock.

R 15 A 1-bit number indicating that this is a repeat packet: the data
has been defined in a previous packet. A server may choose to
skip repeat packets to help it catch up when it is behind in its
transmission of packets. All repeated packets for a given packet
must live in the same hint sample.

All undefined bits are reserved and must be set to 0.

Entry count
A 16-bit unsigned integer specifying the number of entries in the data table.

Extra information TLVs
The extra information TLVs are only present if and only if the X bit is set in the flags field
above. This provides a way of extending the hint track format without changing the version,
while allowing backward compatibility.

Extra information TLVs Bytes

Extra information size 4

TLV size 4

TLV type 4

TLV data Padded to 4-byte boundary(int(TLV Size -8 +3) / 4 *
4

TLV size 4

TLV type 4

TLV data Padded to 4-byte boundary(int(TLV Size -8 +3) / 4 *
4

TLV size and so forth ...

Extra information size
A 32-bit number that is the total size of all extra information TLVs in this packet, including the
4 bytes used for this field. An empty Extra information TLVs table would just be the Extra
information size, having the value 4. (In this case, it would be more efficient simply to not set
the X bit and save 4 bytes just to represent the empty table.)


C H A P T E R 3

TLV size
A 32-bit number that is the total size of this one TLV entry, including 4 bytes for the size, 4
bytes for the type, and any data bytes, but not including padding required to align to the next
4 byte boundary.

TLV type
A 32-bit tag (a four-character OSType) identifying the TLV. Servers must ignore TLV types that
they do not recognize. Note that TLV types containing all lowercase letters are reserved by
Apple Computer.

TLV data
The data for the TLV.

In order to support MPEG (and other data types) whose RTP timestamp is not monotonically increasing
and directly calculated from the sample timestamp, the following TLV type is defined:

Size Type Data Description

12 'rtpo' A signed 32-bit integer, which is to be added to the RTP
timestamp, which is derived from the hint sample timestamp.

Data table
A table that defines the data to be put in the payload portion of the RTP packet. This table
defines various places the data can be retrieved.
Data table entry Bytes

Data source 1

Data 15

The data source field of the entry table indicates how the other 15 bytes of the entry are to be
interpreted. Values of 0 through 4 are defined. The various data table formats are defined below.

Although there are various schemes, note that the entries in the various schemes are the same size,
16 bytes long.

No-Op Data Mode
The data table entry has the following format for no-op mode.

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
data source = 0 ignored
ignored

Field descriptions

Data source = 0
A value of 0 indicates that this data table entry is to be ignored.


C H A P T E R 3

Immediate Data Mode
The data table entry has the following format for immediate mode.

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
data source = 1 immediate length

immediate data

Field descriptions

Data source = 1
A value of one indicates that the data is to be immediately taken from the bytes of data that
follow.

Immediate length
An 8-bit integer indicating the number of bytes to take from the data that follows. Legal values
range from 0 to 14.

Immediate data
14 bytes of data to place into the payload portion of the packet. Only the first number of bytes
indicated by the immediate length field are used.

Sample Mode
The data table entry has the following format for sample mode.

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
data source = 2 track ref index
length

sample number

offset

bytes per compression block
samples per compression block

Field descriptions

Data source = 2
A value of two indicates that the data is to be taken from a track’s sample data.


C H A P T E R 3

Track ref index
A value that indicates which track the sample data will come from. A value of zero means that
there is exactly one media track referenced, so use that. Values from 1 to 127 are indexes into
the hint track reference atom entries, indicating which original media track the sample is to be
read from. A value of -1 means the hint track itself, that is, get the sample from the same track
as the hint sample you are currently parsing.

Length
A 16-bit integer specifying the number of bytes in the sample to copy.

Sample number
A 32-bit integer specifying sample number of the track.

Offset
A 32-bit integer specifying the offset from the start of the sample from which to start copying.
If you are referencing samples in the hint track, this will generally points into the Additional
Data area.

Bytes per compression block
A 16-bit unsigned integer specifying the number of bytes that results from compressing the
number of samples in the Samples per compression block field. A value of 0 is equivalent to
a value of 1.

Samples per compression block
A 16-bit unsigned integer specifying the uncompressed samples per compression block. A
value of 0 is equivalent to a value of 1.

If the bytes per compression block and/or the samples per compression block is greater than 1, than
this ratio is used to translate a sample number into an actual byte offset.

This ratio mode is typically used for compressed audio tracks. Note that for QuickTime sound tracks,
the bytes per compression block also factors in the number of sound channels in that stream, so a
QuickTime stereo sound stream’s BPCB would be twice that of a mono stream of the same sound
format.

(CB = NS * BPCB / SPCB)

where CB = compressed bytes, NS = number of samples, BPCB = bytes per compression block, and
SPCB = samples per compression block.

An example:

A GSM compression block is typically 160 samples packed into 33 bytes.

So, BPCB = 33 and SPCB = 160.

The hint sample requests 33 bytes of data starting at the 161st media sample. Assume that the first
QuickTime chunk contains at least 320 samples. So after determining that this data will come from
chunk 1, and where chunk 1 starts, you must use this ratio to adjust the offset into the file where the
requested samples will be found:

chunk_number = 1; /* calculated by walking the sample-to-chunk atom */
first_sample_in_this_chunk = 1; /* also calculated from that atom */


C H A P T E R 3

chunk_offset = chunk_offsets[chunk_number]; /* from the stco atom */
data_offset = (sample_number - first_sample_in_this_chunk) * BPCB / SPCB;
read_from_file(chunk_offset + data_offset, length); /* read our data */

Sample Description Mode
The data table entry has the following format for sample description mode.

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
data source = 3 track ref index
length

sample description index

offset

reserved

Field descriptions

Data source = 3
A value of three indicates that the data is to be taken from the media track's sample description
table.

Track ref index
A value that indicates which track the sample description will come from. A value of 0 means
that there is exactly one hint track reference, so use that. Values from 1 to 127 are indexes into
the hint track reference atom entries, indicating which original media track the sample is to be
read from. A value of -1 means the hint track itself, that is, get the sample description from the
same track as the hint sample you are currently parsing.

Length
A 16-bit integer specifying the number of bytes to copy.

Sample description index
A 32-bit integer specifying the index into the media's sample description table.

Offset
A 32-bit integer specifying the offset from the start of the sample description from which to
start copying.

Reserved
Four bytes that must be set to 0.

Additional data
A variable length field containing data pointed to by hint track sample mode entries in the
data table.


C H A P T E R 3

VR Media

This section describes the QuickTime VR world and node information atom containers, which can
be obtained by calling the QuickTime VR Manager routines QTVRGetVRWorld and QTVRGetNodeInfo.
Those routines, as well as a complete discussion of QuickTime VR and how your application can
create QuickTime VR movies, are described in detail in Programming With QuickTime VR, available
at http://developer.apple.com/documentation/Quicktime/Quicktime.html.

Many atom types contained in the VR world and node information atom containers are unique within
their container. For example, each has a single header atom. Most parent atoms within an atom
container are unique as well, such as the node parent atom in the VR world atom container or the hot
spot parent atom in the node information atom container. For these one-time-only atoms, the atom
ID is always set to 1. Unless otherwise mentioned in the descriptions of the atoms that follow, assume
that the atom ID is 1.

Note that many atom structures contain two version fields, majorVersion and minorVersion. The
values of these fields correspond to the constants kQTVRMajorVersion and kQTVRMinorVersion
found in the header file QuickTimeVRFormat.h. For QuickTime 2.0 files, these values are 2 and 0.

QuickTime provides a number of routines for both creating and accessing atom containers.

Some of the leaf atoms within the VR world and node information atom containers contain fields that
specify the ID of string atoms that are siblings of the leaf atom. For example, the VR world header
atom contains a field for the name of the scene. The string atom is a leaf atom whose atom type is
kQTVRStringAtomType ('vrsg'). Its atom ID is that specified by the referring leaf atom.

A string atom contains a string. The structure of a string atom is defined by the QTVRStringAtom data
type:

typedef struct QTVRStringAtom {
UInt16 stringUsage;
UInt16 stringLength;
unsigned char theString[4];
} QTVRStringAtom, *QTVRStringAtomPtr;

Field descriptions

stringUsage
The string usage. This field is unused.

stringLength
The length, in bytes, of the string.

theString
The string. The string atom structure is extended to hold this string.

Each string atom may also have a sibling leaf atom called the string encoding atom. The string encoding
atom’s atom type is kQTVRStringEncodingAtomType ('vrse'). Its atom ID is the same as that of the
corresponding string atom. The string encoding atom contains a single variable, TextEncoding, a
UInt32, as defined in the header file TextCommon.h. The value of TextEncoding is handed, along
with the string, to the routine QTTextToNativeText for conversion for display on the current machine.
The routine QTTextToNativeText is found in the header file Movies.h.

VR Media 163

C H A P T E R 3

Note: The header file TextCommon.h contains constants and routines for generating and handling
text encodings. <8bat>u

VR World Atom Container
The VR world atom container (VR world for short) includes such information as the name for the
entire scene, the default node ID, and default imaging properties, as well as a list of the nodes contained
in the QTVR track.

A VR world can also contain custom scene information. QuickTime VR ignores any atom types that
it doesn’t recognize, but you can extract those atoms from the VR world using standard QuickTime
atom functions.

The structure of the VR world atom container is shown in Figure 3-6 (page 164). The component atoms
are defined and their structures are shown in the sections that follow.

Figure 3-6 Structure of the VR world atom container

VR world

VR world header

Name string

Imaging parent

Panorama imaging

Panorama imaging

Node parent

Node ID

Node location

Node ID

Node location

Cursor parent

Cursor

Color cursor

VR World Header Atom Structure

The VR world header atom is a leaf atom. Its atom type is kQTVRWorldHeaderAtomType ('vrsc'). It
contains the name of the scene and the default node ID to be used when the file is first opened as well
as fields reserved for future use.

164 VR Media

C H A P T E R 3

The structure of a VR world header atom is defined by the QTVRWorldHeaderAtom data type:

typedef struct VRWorldHeaderAtom {
UInt16 majorVersion;
UInt16 minorVersion;
QTAtomID nameAtomID;
UInt32 defaultNodeID;
UInt32 vrWorldFlags;
UInt32 reserved1;
UInt32 reserved2;
} VRWorldHeaderAtom, *QTVRWorldHeaderAtomPtr;
QT
QT

Field descriptions

majorVersion
The major version number of the file format.

minorVersion
The minor version number of the file format.

nameAtomID
The ID of the string atom that contains the name of the scene. That atom should be a sibling
of the VR world header atom. The value of this field is 0 if no name string atom exists.

defaultNodeID
The ID of the default node (that is, the node to be displayed when the file is first opened).

vrWorldFlags
A set of flags for the VR world. This field is unused.

reserved1
Reserved. This field must be 0.

reserved2

Imaging Parent Atom

The imaging parent atom is the parent atom of one or more node-specific imaging atoms. Its atom
type is kQTVRImagingParentAtomType ('imgp'). Only panoramas have an imaging atom defined.

Panorama-Imaging Atom

A panorama-imaging atom describes the default imaging characteristics for all the panoramic nodes
in a scene. This atom overrides QuickTime VR’s own defaults.

The panorama-imaging atom has an atom type of kQTVRPanoImagingAtomType ('impn'). Generally,
there is one panorama-imaging atom for each imaging mode, so the atom ID, while it must be unique
for each atom, is ignored. QuickTime VR iterates through all the panorama-imaging atoms.

VR Media 165

C H A P T E R 3

The structure of a panorama-imaging atom is defined by the QTVRPanoImagingAtom data type:

typedef struct QTVRPanoImagingAtom {
UInt32 imagingMode;
UInt32 imagingValidFlags;
UInt32 correction;
UInt32 quality;
UInt32 directDraw;
UInt32 imagingProperties[6];
UInt32 reserved1;
UInt32 reserved2;
} QTVRPanoImagingAtom, *VRPanoImagingAtomPtr;

Field descriptions

majorVersion

minorVersion

imagingMode
The imaging mode to which the default values apply. Only kQTVRStatic and kQTVRMotion
are allowed here.

imagingValidFlags
A set of flags that indicate which imaging property fields in this structure are valid.

correction
The default correction mode for panoramic nodes. This can be either kQTVRNoCorrection,
kQTVRPartialCorrection, or kQTVRFullCorrection.

quality
The default imaging quality for panoramic nodes.

directDraw
The default direct-drawing property for panoramic nodes. This can be true or false.

imagingProperties
Reserved for future panorama-imaging properties.

reserved1

reserved2

The imagingValidFlags field in the panorama-imaging atom structure specifies which imaging
property fields in that structure are valid. You can use these bit flags to specify a value for that field:

166 VR Media

C H A P T E R 3

enum {
kQTVRValidCorrection = 1 << 0,
kQTVRValidQuality = 1 << 1,
kQTVRValidDirectDraw = 1 << 2,
kQTVRValidFirstExtraProperty = 1 << 3
};


kQTVRValidCorrection
If this bit is set, the correction field holds a default correction mode.

kQTVRValidQuality
If this bit is set, the quality field holds a default imaging quality.

kQTVRValidDirectDraw
If this bit is set, the directDraw field holds a default direct-drawing property.

kQTVRValidFirstExtraProperty
If this bit is set, the first element in the array in the imagingProperties field holds a default
imaging property. As new imaging properties are added, they will be stored in this array.

Node Parent Atom

The node parent atom is the parent of one or more node ID atoms. The atom type of the node parent
atom is kQTVRNodeParentAtomType ('vrnp') and the atom type of the each node ID atom is
kQTVRNodeIDAtomType ('vrni').

There is one node ID atom for each node in the file. The atom ID of the node ID atom is the node ID
of the node. The node ID atom is the parent of the node location atom. The node location atom is the
only child atom defined for the node ID atom. Its atom type is kQTVRNodeLocationAtomType ('nloc').

Node Location Atom Structure

The node location atom is the only child atom defined for the node ID atom. Its atom type is
kQTVRNodeLocationAtomType ('nloc'). A node location atom describes the type of a node and its
location.

The structure of a node location atom is defined by the QTVRNodeLocationAtom data type:

typedef struct VRNodeLocationAtom {
OSType nodeType;
UInt32 locationFlags;
UInt32 locationData;
UInt32 reserved1;
UInt32 reserved2;

Node Parent Atom 167

C H A P T E R 3

} VRNodeLocationAtom, *QTVRNodeLocationAtomPtr;
QT
QT

Field descriptions

majorVersion

minorVersion

nodeType
The node type. This field should contain either kQTVRPanoramaType or kQTVRObjectType.

locationFlags
The location flags. This field must contain the value kQTVRSameFile, indicating that the node
is to be found in the current file. In future, these flags may indicate that the node is in a different
file or at some URL location.

locationData
The location of the node data. When the locationFlags field is kQTVRSameFile, this field
should be 0. The nodes are found in the file in the same order that they are found in the node
list.

reserved1

reserved2

Custom Cursor Atoms

The hot spot information atom, discussed in “Hot Spot Information Atom” (page 171), allows you to
indicate custom cursor IDs for particular hot spots that replace the default cursors used by QuickTime
VR. QuickTime VR allows you to store your custom cursors in the VR world of the movie file.

Note: If you’re using the Mac OS, you could store your custom cursors in the resource fork of the
movie file. However, this would not work on any other platform (such as Windows), so storing cursors
in the resource fork of the movie file is not recommended. <8bat>u

The cursor parent atom is the parent of all of the custom cursor atoms stored in the VR world. Its
atom type is kQTVRCursorParentAtomType ('vrcp'). The child atoms of the cursor parent are either
cursor atoms or color cursor atoms. Their atom types are kQTVRCursorAtomType ('CURS') and
kQTVRColorCursorAtomType ('crsr'). These atoms are stored exactly as cursors or color cursors
would be stored as a resource.

168 Custom Cursor Atoms

C H A P T E R 3

Node Information Atom Container

The node information atom container includes general information about the node such as the node’s
type, ID, and name. The node information atom container also contains the list of hot spot atoms for
the node. A QuickTime VR movie contains one node information atom container for each node in the
file. The routine QTVRGetNodeInfo allows you to obtain the node information atom container for the
current node or for any other node in the movie.

Figure 3-7 (page 169) shows the structure of the node information atom container.

Figure 3-7 Structure of the node information atom container

Node Information

Node header

Name string

Comment string

Hot spot parent

Hot spot

Hot spot information

Name string

Comment string

Link hot spot information

Hot spot

Hot spot information

Name string

Comment string

URL hot spot information

Node Header Atom Structure
A node header atom is a leaf atom that describes the type and ID of a node, as well as other information
about the node. Its atom type is kQTVRNodeHeaderAtomType ('ndhd').

The structure of a node header atom is defined by the QTVRNodeHeaderAtom data type:

typedef struct VRNodeHeaderAtom {
OSType nodeType;
QTAtomID nodeID;


C H A P T E R 3

QTAtomID commentAtomID;
UInt32 reserved1;
UInt32 reserved2;
} VRNodeHeaderAtom, *VRNodeHeaderAtomPtr;
QT
QT

Field descriptions

majorVersion

minorVersion

nodeType
The node type. This field should contain either kQTVRPanoramaType or kQTVRObjectType.

nodeID
The node ID.

nameAtomID
The ID of the string atom that contains the name of the node. This atom should be a sibling of
the node header atom. The value of this field is 0 if no name string atom exists.

commentAtomID
The ID of the string atom that contains a comment for the node. This atom should be a sibling
of the node header atom. The value of this field is 0 if no comment string atom exists.

reserved1

reserved2

Hot Spot Parent Atom
The hot spot parent atom is the parent for all hot spot atoms for the node. The atom type of the hot
spot parent atom is kQTVRHotSpotParentAtomType ('hspa') and the atom type of the each hot spot
atom is kQTVRHotSpotAtomType ('hots'). The atom ID of each hot spot atom is the hot spot ID for
the corresponding hot spot. The hot spot ID is determined by its color index value as it is stored in
the hot spot image track.

The hot spot track is an 8-bit video track that contains color information that indicates hot spots. For
more information, refer to Programming With QuickTime VR.

Each hot spot atom is the parent of a number of atoms that contain information about each hot spot.

170 Node Information Atom Container

C H A P T E R 3

Hot Spot Information Atom
The hot spot information atom contains general information about a hot spot. Its atom type is
kQTVRHotSpotInfoAtomType ('hsin'). Every hot spot atom should have a hot spot information atom
as a child.

The structure of a hot spot information atom is defined by the QTVRHotSpotInfoAtom data type:

typedef struct VRHotSpotInfoAtom {
OSType hotSpotType;
SInt32 cursorID[3];
Float32 bestPan;
Float32 bestTilt;
Float32 bestFOV;
FloatPoint bestViewCenter;
Rect hotSpotRect;
UInt32 flags;
UInt32 reserved1;
UInt32 reserved2;
} VRHotSpotInfoAtom, *QTVRHotSpotInfoAtomPtr;
QT
QT

Field descriptions

majorVersion

minorVersion

hotSpotType
The hot spot type. This type specifies which other information atoms—if any—are siblings to
this one. QuickTime VR recognizes three types: kQTVRHotSpotLinkType, kQTVRHotSpotURLType,
and kQTVRHotSpotUndefinedType.

nameAtomID
The ID of the string atom that contains the name of the hot spot. This atom should be a sibling
of the hot spot information atom. This string is displayed in the QuickTime VR controller bar
when the mouse is moved over the hot spot.

commentAtomID
The ID of the string atom that contains a comment for the hot spot. This atom should be a
sibling of the hot spot information atom. The value of this field is 0 if no comment string atom
exists.

cursorID
An array of three IDs for custom hot spot cursors (that is, cursors that override the default hot
spot cursors provided by QuickTime VR). The first ID (cursorID[0]) specifies the cursor that


C H A P T E R 3

is displayed when it is in the hot spot. The second ID (cursorID[1]) specifies the cursor that
is displayed when it is in the hot spot and the mouse button is down. The third ID
(cursorID[2]) specifies the cursor that is displayed when it is in the hot spot and the mouse
button is released. To retain the default cursor for any of these operations, set the corresponding
cursor ID to 0. Custom cursors should be stored in the VR world atom container, as described
in “VR World Atom Container” (page 164).

bestPan
The best pan angle for viewing this hot spot.

bestTilt
The best tilt angle for viewing this hot spot.

bestFOV
The best field of view for viewing this hot spot.

bestViewCenter
The best view center for viewing this hot spot; applies only to object nodes.

hotSpotRect
The boundary box for this hot spot, specified as the number of pixels in full panoramic space.
This field is valid only for panoramic nodes.

flags
A set of hot spot flags. This field is unused.

reserved1

reserved2

Note: In QuickTime VR movie files, all angular values are stored as 32-bit floating-point values that
specify degrees. In addition, all floating-point values conform to the IEEE Standard 754 for binary
floating-point arithmetic, in big-endian format. <8bat>u

Specific Information Atoms
Depending on the value of the hotSpotType field in the hot spot info atom there may also be a type
specific information atom. The atom type of the type-specific atom is the hot spot type.

Link Hot Spot Atom
The link hot spot atom specifies information for hot spots of type kQTVRHotSpotLinkType ('link').
Its atom type is thus 'link'. The link hot spot atom contains specific information about a link hot
spot.


C H A P T E R 3

The structure of a link hot spot atom is defined by the QTVRLinkHotSpotAtom data type:

typedef struct VRLinkHotSpotAtom {
UInt32 toNodeID;
UInt32 fromValidFlags;
Float32 fromPan;
Float32 fromTilt;
Float32 fromFOV;
FloatPoint fromViewCenter;
UInt32 toValidFlags;
Float32 toPan;
Float32 toTilt;
Float32 toFOV;
FloatPoint toViewCenter;
Float32 distance;
UInt32 flags;
UInt32 reserved1;
UInt32 reserved2;
} VRLinkHotSpotAtom, *VRLinkHotSpotAtomPtr;
QT

Field descriptions

majorVersion

minorVersion

toNodeID
The ID of the destination node (that is, the node to which this hot spot is linked).

fromValidFlags
A set of flags that indicate which source node view settings are valid.

fromPan
The preferred from-pan angle at the source node (that is, the node containing the hot spot).

fromTilt
The preferred from-tilt angle at the source node.

fromFOV
The preferred from-field of view at the source node.

fromViewCenter
The preferred from-view center at the source node.

toValidFlags
A set of flags that indicate which destination node view settings are valid.


C H A P T E R 3

toPan
The pan angle to use when displaying the destination node.

toTilt
The tilt angle to use when displaying the destination node.

toFOV
The field of view to use when displaying the destination node.

toViewCenter
The view center to use when displaying the destination node.

distance
The distance between the source node and the destination node.

flags
A set of link hot spot flags. This field is unused and should be set to 0.

reserved1

reserved2

Certain fields in the link hot spot atom are not used by QuickTime VR. The fromValidFlags field is
generally set to 0 and the other from fields are not used. However, these fields could be quite useful
if you have created a transition movie from one node to another. The from angles can be used to
swing the current view of the source node to align with the first frame of the transition movie. The
distance field is intended for use with 3D applications, but is also not used by QuickTime VR.

Link Hot Spot Valid Flags

The toValidFlags field in the link hot spot atom structure specifies which view settings are to be
used when moving to a destination node from a hot spot. You can use these bit flags to specify a value
for that field:

enum {
kQTVRValidPan = 1 << 0,
kQTVRValidTilt = 1 << 1,
kQTVRValidFOV = 1 << 2,
kQTVRValidViewCenter = 1 << 3
};


kQTVRValidPan
If this bit is set, the destination pan angle is used.

kQTVRValidTilt
If this bit is set, the destination tilt angle is used.


C H A P T E R 3

kQTVRValidFOV
If this bit is set, the destination field of view is used.

kQTVRValidViewCenter
If this bit is set, the destination view center is used.

URL Hot Spot Atom

The URL hot spot atom has an atom type of kQTVRHotSpotURLType ('url '). The URL hot spot atom
contains a URL string for a particular Web location (for example, http://quicktimevr.apple.com).
QuickTime VR automatically links to this URL when the hot spot is clicked.

Support for Wired Actions

Certain actions on a QuickTime VR movie can trigger wired actions if the appropriate event handler
atoms have been added to the file. This section discusses what atoms must be included in the
QuickTime VR file to support wired actions.

As with sprite tracks, the presence of a certain atom in the media property atom container of the
QTVR track enables the handling of wired actions. This atom is of type
kSpriteTrackPropertyHasActions, which has a single Boolean value that must be set to true.

When certain events occur and the appropriate event handler atom is found in the QTVR file, then
that atom is passed to QuickTime to perform any actions specified in the atom. The event handler
atoms themselves must be added to the node information atom container in the QTVR track. There
are two types of event handlers for QTVR nodes: global and hot spot specific. The currently supported
global event handlers are kQTEventFrameLoaded and kQTEventIdle. The event handler atoms for
these are located at the root level of the node information atom container. A global event handler
atom’s type is set to the event type and its ID is set to 1.

Hot spot–specific event handler atoms are located in the specific hot spot atom as a sibling to the hot
spot info atom. For these atoms, the atom type is always kQTEventType and the ID is the event type.
Supported hot spot–specific event types are kQTEventMouseClick, kQTEventMouseClickEnd,
kQTEventMouseClickEndTriggerButton, and kQTEventMouseEnter, kQTEventMouseExit.

The specific actions that cause these events to be generated are described as follows:

kQTEventFrameLoaded ('fram')
Generated when a node is entered, before any application-installed entering-node procedure
is called (this event processing is considered part of the node setup that occurs before the
application’s routine is called).

kQTEventIdle ('idle')
Generated every n ticks, where n is defined by the contents of the
kSpriteTrackPropertyQTIdleEventsFrequency atom (SInt32) in the media property atom
container. When appropriate, this event is triggered before any normal idle processing occurs
for the QuickTime VR movie.

URL Hot Spot Atom 175

C H A P T E R 3

kQTEventMouseClick ('clik')
Generated when the mouse goes down over a hot spot.

kQTEventMouseClickEnd ('cend')
Generated when the mouse goes up after a kQTEventMouseClick is generated, regardless of
whether the mouse is still over the hot spot originally clicked. This event occurs prior to
QuickTime VR’s normal mouse-up processing.

kQTEventMouseClickEndTriggerButton ('trig')
Generated when a click end triggers a hot spot (using the same criterion as used by QuickTime
VR in 2.1 for link/url hot spot execution). This event occurs prior to QuickTime VR’s normal
hot spot–trigger processing.

kQTEventMouseEnter ('entr'), kQTEventMouseExit ('exit')
These two events are generated when the mouse rolls into or out of a hot spot, respectively.
These events occur whether or not the mouse is down and whether or not the movie is being
panned. These events occur after any application-installed MouseOverHotSpotProc is called,
and will be cancelled if the return value from the application’s routine indicates that
QuickTimeVR’s normal over–hot spot processing should not take place.

QuickTime VR File Format

A QuickTime VR movie is stored on disk in a format known as the QuickTime VR file format. Beginning
in QuickTime VR 2.0, a QuickTime VR movie could contain one or more nodes. Each node is either
a panorama or an object. In addition, a QuickTime VR movie could contain various types of hot spots,
including links between any two types of nodes.

Important: This section describes the file format supported by version 2.1 of the QuickTime VR
Manager. For information on the file format supported by earlier versions of QuickTime VR, see
Macintosh Technotes numbers 1035 and 1036. The Macintosh Technotes are available electronically
on the Developer CD Series and on the Technote website at
http://devworld.apple.com/dev/technotes.shtml s

All QuickTime VR movies contain a single QTVR track, a special type of QuickTime track that maintains
a list of the nodes in the movie. Each individual sample in a QTVR track contains general information
and hot spot information for a particular node.

If a QuickTime VR movie contains any panoramic nodes, that movie also contains a single panorama
track, and if it contains any object nodes, it also contains a single object track. The panorama and
object tracks contain information specific to the panoramas or objects in the movie. The actual image
data for both panoramas and objects is usually stored in standard QuickTime video tracks, hereafter
referred to as image tracks. (An image track can also be any type of track that is capable of displaying
an image, such as a QuickTime 3D track.) The individual frames in the image track for a panorama
make up the diced frames of the original single panoramic image. The frames for the image track of
an object represent the many different views of the object. Hot spot image data is stored in parallel
video tracks for both panoramas and objects.

176 QuickTime VR File Format

C H A P T E R 3

Single-Node Panoramic Movies
Figure 3-8 (page 177) illustrates the basic structure of a single-node panoramic movie. As you can see,
every panoramic movie contains at least three tracks: a QTVR track, a panorama track, and a panorama
image track.

Figure 3-8 The structure of a single-node panoramic movie file

QTVR track

Panorama track

Panorama image track

For a single-node panoramic movie, the QTVR track contains just one sample. There is a corresponding
sample in the panorama track, whose time and duration are the same as the time and duration of the
sample in the QTVR track. The time base of the movie is used to locate the proper video samples in
the panorama image track. For a panoramic movie, the video sample for the first diced frame of a
node’s panoramic image is located at the same time as the corresponding QTVR and panorama track
samples. The total duration of all the video samples is the same as the duration of the corresponding
QTVR sample and the panorama sample.

A panoramic movie can contain an optional hot spot image track and any number of standard
QuickTime tracks. A panoramic movie can also contain panoramic image tracks with a lower resolution.
The video samples in these low-resolution image tracks must be located at the same time and must
have the same total duration as the QTVR track. Likewise, the video samples for a hot spot image
track, if one exists, must be located at the same time and must have the same total duration as the
QTVR track.

Single-Node Object Movies
Figure 3-9 (page 177) illustrates the basic structure of a single-node object movie. As you can see, every
object movie contains at least three tracks: a QTVR track, an object track, and an object image track.

Figure 3-9 The structure of a single-node object movie file

QTVR track

Object track

Object image track

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For a single-node object movie, the QTVR track contains just one sample. There is a corresponding
sample in the object track, whose time and duration are the same as the time and duration of the
sample in the QTVR track. The time base of the movie is used to locate the proper video samples in
the object image track.

For an object movie, the frame corresponding to the first row and column in the object image array
is located at the same time as the corresponding QTVR and object track samples. The total duration
of all the video samples is the same as the duration of the corresponding QTVR sample and the object
sample.

In addition to these three required tracks, an object movie can also contain a hot spot image track and
any number of standard QuickTime tracks (such as video, sound, and text tracks). A hot spot image
track for an object is a QuickTime video track that contains images of colored regions delineating the
hot spots; an image in the hot spot image track must be synchronized to match the appropriate image
in the object image track. A hot spot image track should be 8 bits deep and can be compressed with
any lossless compressor (including temporal compressors). This is also true of panoramas.

Note: To assign a single fixed-position hot spot to all views of an object, you should create a hot spot
image track that consists of a single video frame whose duration is the entire node time. <8bat>u

To play a time-based track with the object movie, you must synchronize the sample data of that track
to the start and stop times of a view in the object image track. For example, to play a different sound
with each view of an object, you might store a sound track in the movie file with each set of sound
samples synchronized to play at the same time as the corresponding object’s view image. (This
technique also works for video samples.) Another way to add sound or video is simply to play a
sound or video track during the object’s view animation; to do this, you need to add an active track
to the object that is equal in duration to the object’s row duration.

Important: In a QuickTime VR movie file, the panorama image tracks and panorama hot spot tracks
must be disabled. For an object, the object image tracks must be enabled and the object hot spot tracks
must be disabled. <8bat>s

Multinode Movies
A multinode QuickTime VR movie can contain any number of object and panoramic nodes. Figure
3-10 (page 179) illustrates the structure of a QuickTime VR movie that contains five nodes (in this case,
three panoramic nodes and two object nodes).

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Figure 3-10 The structure of a multinode movie file

QTVR track 1st node 2nd node 3rd node 4th node 5th node

Panorama track

Panorama image track
Panorama low-res
image track
Panorama hot spot
image track
Object track

Object image track

Object hot spot track

Important: Panoramic tracks and object tracks must never be located at the same time. <8bat>s

QTVR Track

A QTVR track is a special type of QuickTime track that maintains a list of all the nodes in a movie.
The media type for a QTVR track is 'qtvr'. All the media samples in a QTVR track share a common
sample description. This sample description contains the VR world atom container. The track contains
one media sample for each node in the movie. Each QuickTime VR media sample contains a node
information atom container.

QuickTime VR Sample Description Structure
Whereas the QuickTime VR media sample is simply the node information itself, all sample descriptions
are required by QuickTime to have a certain structure for the first several bytes. The structure for the
QuickTime VR sample description is as follows:

typedef struct QTVRSampleDescription {
UInt32 size;
UInt32 type;
UInt32 reserved1;
UInt16 reserved2;
UInt16 dataRefIndex;
UInt32 data;
} QTVRSampleDescription, *QTVRSampleDescriptionPtr, **QTVRSampleDescriptionHandle;

Field descriptions

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size
The size, in bytes, of the sample description header structure, including the VR world atom
container contained in the data field.

type
The sample description type. For QuickTime VR movies, this type should be 'qtvr'.

reserved1

reserved2

dataRefIndex

data
The VR world atom container. The sample description structure is extended to hold this atom
container.

Panorama Tracks

A movie’s panorama track is a track that contains information about the panoramic nodes in a scene.
The media type of the panorama track is 'pano'. Each sample in a panorama track corresponds to a
single panoramic node. This sample parallels the corresponding sample in the QTVR track. Panorama
tracks do not have a sample description (although QuickTime requires that you specify a dummy
sample description when you call AddMediaSample to add a sample to a panorama track). The sample
itself contains an atom container that includes a panorama sample atom and other optional atoms.

Panorama Sample Atom Structure
A panorama sample atom has an atom type of kQTVRPanoSampleDataAtomType ('pdat'). It describes
a single panorama, including track reference indexes of the scene and hot spot tracks and information
about the default viewing angles and the source panoramic image.

The structure of a panorama sample atom is defined by the QTVRPanoSampleAtom data type:

typedef struct VRPanoSampleAtom {
UInt32 imageRefTrackIndex;
UInt32 hotSpotRefTrackIndex;
Float32 minPan;
Float32 maxPan;
Float32 minTilt;
Float32 maxTilt;
Float32 minFieldOfView;
Float32 maxFieldOfView;

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Float32 defaultPan;
Float32 defaultTilt;
Float32 defaultFieldOfView;
UInt32 imageSizeX;
UInt32 imageSizeY;
UInt16 imageNumFramesX;
UInt16 imageNumFramesY;
UInt32 hotSpotSizeX;
UInt32 hotSpotSizeY;
UInt16 hotSpotNumFramesX;
UInt16 hotSpotNumFramesY;
UInt32 flags;
OSType panoType;
UInt32 reserved2;
} VRPanoSampleAtom, *VRPanoSampleAtomPtr;
QT
QT
QT

Field descriptions

majorVersion

minorVersion

imageRefTrackIndex
The index of the image track reference. This is the index returned by the AddTrackReference
function when the image track is added as a reference to the panorama track. There can be
more than one image track for a given panorama track and hence multiple references. (A
panorama track might have multiple image tracks if the panoramas have different characteristics,
which could occur if the panoramas were shot with different size camera lenses.) The value in
this field is 0 if there is no corresponding image track.

hotSpotRefTrackIndex
The index of the hot spot track reference.

minPan
The minimum pan angle, in degrees. For a full panorama, the value of this field is usually 0.0.

maxPan
The maximum pan angle, in degrees. For a full panorama, the value of this field is usually
360.0.

minTilt
The minimum tilt angle, in degrees. For a high-resolution panorama, a typical value for this
field is –42.5.

maxTilt
The maximum tilt angle, in degrees. For a high-resolution panorama, a typical value for this
field is +42.5.

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minFieldOfView
The minimum vertical field of view, in degrees. For a high-resolution panorama, a typical
value for this field is 5.0. The value in this field is 0 for the default minimum field of view,
which is 5 percent of the maximum field of view.

maxFieldOfView
The maximum vertical field of view, in degrees. For a high-resolution panorama, a typical
value for this field is 85.0. The value in this field is 0 for the default maximum field of view,
which is maxTilt – minTilt.

defaultPan
The default pan angle, in degrees.

defaultTilt
The default tilt angle, in degrees.

defaultFieldOfView
The default vertical field of view, in degrees.

imageSizeX
The width, in pixels, of the panorama stored in the highest resolution image track.

imageSizeY
The height, in pixels, of the panorama stored in the highest resolution image track.

imageNumFramesX
The number of frames into which the panoramic image is diced horizontally. The width of
each frame (which is imageSizeX/imageNumFramesX) should be divisible by 4.

imageNumFramesY
The number of frames into which the panoramic image is diced vertically. The height of each
frame (which is imageSizeY/imageNumFramesY) should be divisible by 4.

hotSpotSizeX
The width, in pixels, of the panorama stored in the highest resolution hot spot image track.

hotSpotSizeY
The height, in pixels, of the panorama stored in the highest resolution hot spot image track.

hotSpotNumFramesX
The number of frames into which the panoramic image is diced horizontally for the hot spot
image track.

hotSpotNumFramesY
The number of frames into which the panoramic image is diced vertically for the hot spot
image track.

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flags
A set of panorama flags. kQTVRPanoFlagHorizontal has been superseded by the panoType
field. It is only used when the panoType field is nil to indicate a horizontally-oriented cylindrical
panorama. kQTVRPanoFlagAlwaysWrap is set if the panorama should wrap horizontally,
regardless of whether or not the pan range is 360 degrees. Note that these flags are currently
supported only under Mac OS X.

panoType
An OSType describing the type of panorama. Types supported are
kQTVRHorizontalCylinder

kQTVRVerticalCylinder

kQTVRCube

reserved2

Important: A new flag has been added to the flags field of the QTVRPanoSampleAtom data
structure. This flag controls how panoramas wrap horizontally. If kQTVRPanoFlagAlwaysWrap
is set, then the panorama wraps horizontally, regardless of the number of degrees in the
panorama. If the flag is not set, then the panorama wraps only when the panorama range is
360 degrees. This is the default behavior. s

The minimum and maximum values in the panorama sample atom describe the physical limits of the
panoramic image. QuickTime VR allows you to set further constraints on what portion of the image
a user can see by calling the QTVRSetConstraints routine. You can also preset image constraints by
adding constraint atoms to the panorama sample atom container. The three constraint atom types
are kQTVRPanConstraintAtomType, kQTVRTiltConstraintAtomType, and
kQTVRFOVConstraintAtomType. Each of these atom types share a common structure defined by the
QTVRAngleRangeAtom data type:

typedef struct QTVRAngleRangeAtom {
Float32 minimumAngle;
Float32 maximumAngle;
} QTVRAngleRangeAtom, *QTVRAngleRangeAtomPtr;

Field descriptions

minimumAngle
The minimum angle in the range, in degrees.

maximumAngle
The maximum angle in the range, in degrees.

Panorama Image Track
The actual panoramic image for a panoramic node is contained in a panorama image track, which is
a standard QuickTime video track. The track reference to this track is stored in the
imageRefTrackIndex field of the panorama sample atom.

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QuickTime VR 2.1 required the original panoramic image to be rotated 90 degrees counterclockwise.
This orientation has changed in QuickTime VR 2.2, however, as discussed later in this section.

The rotated image is diced into smaller frames, and each diced frame is then compressed and added
to the video track as a video sample, as shown in Figure 3-11 (page 184). Frames can be compressed
using any spatial compressor; however, temporal compression is not allowed for panoramic image
tracks.

Figure 3-11 Creating an image track for a panorama

Original panorama

Rotate 90 0 CCW Image track
1 1
2
2
3
3

Dice Add
the samples
image to image
track

24
24

QuickTime VR 2.2 does not require the original panoramic image to be rotated 90 degrees
counterclockwise, as was the case in QuickTime VR 2.1. The rotated image is still diced into smaller
frames, and each diced frame is then compressed and added to the video track as a video sample, as
shown in Figure 3-12 (page 185).

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Figure 3-12 Creating an image track for a panorama, with the image track oriented horizontally

Original panorama

Dice the Image

1 2 3 24

Add samples to image track

Image track

1 2 3 24

In QuickTime 3.0, a panorama sample atom (which contains information about a single panorama)
contains the panoType field, which indicates whether the diced panoramic image is oriented
horizontally or vertically.

Cylindrical Panoramas
The primary change to cylindrical panoramas in QuickTime VR 2.2 is that the panorama, as stored
in the image track of the movie, can be oriented horizontally. This means that the panorama does not
need to be rotated 90 degrees counterclockwise, as required previously.

To indicate a horizontal orientation, the field in the VRPanoSampleAtom data structure formerly called
reserved1 has been renamed panoType. Its type is OSType. The panoType for a horizontally oriented
cylinder is kQTVRHorizontalCylinder (‘hcyl’), while a vertical cylinder is kQTVRVerticalCylinder
(‘vcyl’). For compatibility with older QuickTime VR files, when the panoType field is nil, then a
cylinder is assumed, with the low order bit of the flags field set to 1 to indicate if the cylinder is
horizontal and 0 if the cylinder is vertical.

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One consequence of reorienting the panorama horizontally is that, when the panorama is divided
into separate tiles, the order of the samples in the file is now the reverse of what it was for vertical
cylinders. Since vertical cylinders were rotated 90 degrees counterclockwise, the first tile added to
the image track was the right-most tile in the panorama. For unrotated horizontal cylinders, the first
tile added to the image track is the left-most tile in the panorama.

Cubic Panoramas

A new type of panorama was introduced in the current version of QuickTime: the cubic panorama.
This panorama in its simplest form is represented by six faces of a cube, thus enabling the viewer to
see all the way up and all the way down. The file format and the cubic rendering engine actually
allow for more complicated representations, such as special types of cubes with elongated sides or
cube faces made up of separate tiles. Atoms that describe the orientation of each face allow for these
nonstandard representations. If these atoms are not present, then the simplest representation is
assumed. The following describes this simplest representation: a cube with six square sides.

Tracks in a cubic movie are laid out as they are for cylindrical panoramas. This includes a QTVR track,
a panorama track, and an image track. Optionally, there may also be a hot spot track and a fast-start
preview track. The image, hot spot, and preview tracks are all standard QuickTime video tracks.

Image Tracks in Cubic Nodes
For a cubic node the image track contains six samples that correspond to the six square faces of the
cube. The same applies to hot spot and preview tracks. The following diagram shows how the order
of samples in the track corresponds to the orientation of the cube faces.

Track samples

1 2 3 4 5 6

Cube faces

5

1 2 3 4

6

Note that the frames are oriented horizontally. There is no provision for frames that are rotated 90
counterclockwise as there are for cylindrical panoramas.

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Panorama Tracks in Cubic Nodes

The media sample for a panorama track contains the pano sample atom container. For cubes, some
of the fields in the pano sample data atom have special values, which provide compatibility back to
QuickTime VR 2.2. The cubic projection engine ignores these fields. They allow one to view cubic
movies in older versions of QuickTime VR using the cylindrical engine, although the view will be
somewhat incorrect, and the top and bottom faces will not be visible. The special values are shown
in Table 3-11 (page 187).

Table 3-11 Fields and their special values as represented in the pano sample data atom, providing backward
compatibility to QuickTime VR 2.2

Field Value

imageNumFramesX 4

imageNumFramesY 1

imageSizeX frame width * 4

imageSizeY frame height

minPan 0.0

maxPan 360.0

minTilt -45.0

maxTilt 45.0

minFieldOfView 5.0

maxFieldOfView 90.0

flags 1

A 1 value in the flags field tells QuickTime VR 2.2 that the frames are not rotated. QuickTime VR 2.2
treats this as a four-frame horizontal cylinder. The panoType field (formerly reserved1) must be set
to kQTVRCube (‘cube’) so that QuickTime VR 3.0 can recognize this panorama as a cube.

Since certain viewing fields in the pano sample data atom are being used for backward compatibility,
a new atom must be added to indicate the proper viewing parameters for the cubic image. This atom
is the cubic view atom (atom type ‘cuvw’). The data structure of the cubic view atom is as follows:

struct QTVRCubicViewAtom {
Float32 minPan;
Float32 maxPan;
Float32 minTilt;
Float32 maxTilt;

Float32 defaultPan;

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};
typedef struct QTVRCubicViewAtom QTVRCubicViewAtom;

The fields are filled in as desired for the cubic image. This atom is ignored by older versions of
QuickTime VR. Typical values for the min and max fields are shown in Table 3-12 (page 188).

Table 3-12 Values for min and max fields

Field Value

minPan 0.0

maxPan 360.0

minTilt -90.0

maxTilt 90.0

minFieldOfView 5.0

maxFieldOfView 120.0

You add the cubic view atom to the pano sample atom container (after adding the pano sample data
atom). Then use AddMediaSample to add the atom container to the panorama track.

Nonstandard Cubes

Although the default representation for a cubic panorama is that of six square faces of a cube, it is
possible to depart from this standard representation. When doing so, a new atom must be added to
the pano sample atom container. The atom type is ‘cufa‘. The atom is an array of data structures of
type QTVRCubicFaceData. Each entry in the array describes one face of whatever polyhedron is being
defined. QTVRCubicFaceData is defined as follows:

struct QTVRCubicFaceData {
float orientation[4];
float center[2];
float aspect;
float skew;
};
typedef struct QTVRCubicFaceData QTVRCubicFaceData;

The mathematical explanation of these data structures is beyond the scope of this document but will
be described in a separate Apple Technote. Table 3-13 (page 189) shows what values QuickTime VR
uses for the default representation of six square sides.

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Table 3-13 Values used for representing six square sides

Orientation Orientation Orientation Orientation Center Center Aspect Skew Skew

1 0 0 0 0 0 1 0 # front

–.5 0 .5 0 0 0 1 0 # right

0 0 1 0 0 0 1 0 # back

.5 0 .5 0 0 0 1 0 # left

.5 .5 0 0 0 0 1 0 # top

–.5 .5 0 0 0 0 1 0 # bottom

Hot Spot Image Tracks

When a panorama contains hot spots, the movie file contains a hot spot image track, a video track
that contains a parallel panorama, with the hot spots designated by colored regions. Each diced frame
of the hot spot panoramic image must be compressed with a lossless compressor (such as QuickTime’s
graphics compressor). The dimensions of the hot spot panoramic image are usually the same as those
of the image track’s panoramic image, but this is not required. The dimensions must, however, have
the same aspect ratio as the image track’s panoramic image. A hot spot image track should be 8 bits
deep.

Low-Resolution Image Tracks
It’s possible to store one or more low-resolution versions of a panoramic image in a movie file; those
versions are called low-resolution image tracks. If there is not enough memory at runtime to use the
normal image track, QuickTime VR uses a lower resolution image track if one is available. A
low-resolution image track contains diced frames just like the higher resolution track, but the
reconstructed panoramic image is half the height and half the width of the higher resolution image.

Important: The panoramic images in the lower resolution image tracks and the hot spot image tracks,
if present, must have the same orientation (horizontal or vertical) as the panorama image track.
<8bat>s

Track Reference Entry Structure
Since there are no fields in the pano sample data atom to indicate the presence of low-resolution
image tracks, a separate sibling atom must be added to the panorama sample atom container. The
track reference array atom contains an array of track reference entry structures that specify information
about any low-resolution image tracks contained in a movie. Its atom type is
kQTVRTrackRefArrayAtomType ('tref').

A track reference entry structure is defined by the QTVRTrackRefEntry data type:

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typedef struct QTVRTrackRefEntry {
UInt32 trackRefType;
UInt16 trackResolution;
UInt32 trackRefIndex;
} QTVRTrackRefEntry;

Field descriptions

trackRefType
The track reference type.

trackResolution
The track resolution.

trackRefIndex
The index of the track reference.

The number of entries in the track reference array atom is determined by dividing the size of the atom
by sizeof (QTVRTrackRefEntry).

kQTVRPreviewTrackRes is a special value for the trackResolution field in the QTVRTrackRefEntry
structure. This is used to indicate the presence of a special preview image track.

Object Tracks

A movie’s object track is a track that contains information about the object nodes in a scene. The media
type of the object track is 'obje'. Each sample in an object track corresponds to a single object node
in the scene. The samples of the object track contain information describing the object images stored
in the object image track.

These object information samples parallel the corresponding node samples in the QTVR track and
are equal in time and duration to a particular object node’s image samples in the object’s image track
as well as the object node’s hot spot samples in the object’s hot spot track.

Object tracks do not have a sample description (although QuickTime requires that you specify a
dummy sample description when you call AddMediaSample to add a sample to an object track). The
sample itself is an atom container that contains a single object sample atom and other optional atoms.

Object Sample Atom Structure
object sample atom describes a single object, including information about the default viewing angles
and the view settings. The structure of an object sample atom is defined by the QTVRObjectSampleAtom
data type:

typedef struct VRObjectSampleAtom {
UInt16 movieType;
UInt16 viewStateCount;
UInt16 defaultViewState;

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UInt16 mouseDownViewState;
UInt32 viewDuration;
UInt32 columns;
UInt32 rows;
Float32 mouseMotionScale;
Float32 minPan;
Float32 maxPan;
Float32 defaultPan;
Float32 minTilt;
Float32 maxTilt;
Float32 fieldOfView;
Float32 defaultViewCenterH;
Float32 defaultViewCenterV;
Float32 viewRate;
Float32 frameRate;
UInt32 animationSettings;
UInt32 controlSettings;
} VRObjectSampleAtom, *VRObjectSampleAtomPtr;
QT
QT
QT

Field descriptions

majorVersion

minorVersion

movieType
The movie controller type.

viewStateCount
The number of view states of the object. A view state selects an alternate set of images for an
object’s views. The value of this field must be positive.

defaultViewState
The 1-based index of the default view state. The default view state image for a given view is
displayed when the mouse button is not down.

mouseDownViewState
The 1-based index of the mouse-down view state. The mouse-down view state image for a
given view is displayed while the user holds the mouse button down and the cursor is over
an object movie.

viewDuration
The total movie duration of all image frames contained in an object’s view. In an object that
uses a single frame to represent a view, the duration is the image track’s sample duration time.

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columns
The number of columns in the object image array (that is, the number of horizontal positions
or increments in the range defined by the minimum and maximum pan values). The value of
this field must be positive.

rows
The number of rows in the object image array (that is, the number of vertical positions or
increments in the range defined by the minimum and maximum tilt values). The value of this
field must be positive.

mouseMotionScale
The mouse motion scale factor (that is, the number of degrees that an object is panned or tilted
when the cursor is dragged the entire width of the VR movie image). The default value is 180.0.

minPan
The minimum pan angle, in degrees. The value of this field must be less than the value of the
maxPan field.

maxPan
The maximum pan angle, in degrees. The value of this field must be greater than the value of
the minPan field.

defaultPan
The default pan angle, in degrees. This is the pan angle used when the object is first displayed.
The value of this field must be greater than or equal to the value of the minPan field and less
than or equal to the value of the maxPan field.

minTilt
The minimum tilt angle, in degrees. The default value is +90.0. The value of this field must be
less than the value of the maxTilt field.

maxTilt
The maximum tilt angle, in degrees. The default value is –90.0. The value of this field must be
greater than the value of the minTilt field.

defaultTilt
The default tilt angle, in degrees. This is the tilt angle used when the object is first displayed.
The value of this field must be greater than or equal to the value of the minTilt field and less
than or equal to the value of the maxTilt field.

minFieldOfView
The minimum field of view to which the object can zoom. The valid range for this field is from
1 to the value of the fieldOfView field. The value of this field must be positive.

fieldOfView
The image field of view, in degrees, for the entire object. The value in this field must be greater
than or equal to the value of the minFieldOfView field.

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defaultFieldOfView
The default field of view for the object. This is the field of view used when the object is first
displayed. The value in this field must be greater than or equal to the value of the
minFieldOfView field and less than or equal to the value of the fieldOfView field.

defaultViewCenterH
The default horizontal view center.

defaultViewCenterV
The default vertical view center.

viewRate
The view rate (that is, the positive or negative rate at which the view animation in the object
plays, if view animation is enabled). The value of this field must be from –100.0 through +100.0,
inclusive.

frameRate
The frame rate (that is, the positive or negative rate at which the frame animation in a view
plays, if frame animation is enabled). The value of this field must be from –100.0 through
+100.0, inclusive.

animationSettings
A set of 32-bit flags that encode information about the animation settings of the object.

controlSettings
A set of 32-bit flags that encode information about the control settings of the object.

The movieType field of the object sample atom structure specifies an object controller type, that is,
the user interface to be used to manipulate the object.

QuickTime VR supports the following controller types:

enum ObjectUITypes {
kGrabberScrollerUI = 1,
kOldJoyStickUI = 2,
kJoystickUI = 3,
kGrabberUI = 4,
kAbsoluteUI = 5
};


kGrabberScrollerUI
The default controller, which displays a hand for dragging and rotation arrows when the cursor
is along the edges of the object window.

kOldJoyStickUI
A joystick controller, which displays a joystick-like interface for spinning the object. With this
controller, the direction of panning is reversed from the direction of the grabber.

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kJoystickUI
A joystick controller, which displays a joystick-like interface for spinning the object. With this
controller, the direction of panning is consistent with the direction of the grabber.

kGrabberUI
A grabber-only interface, which displays a hand for dragging but does not display rotation
arrows when the cursor is along the edges of the object window.

kAbsoluteUI
An absolute controller, which displays a finger for pointing. The absolute controller switches
views based on a row-and-column grid mapped into the object window.

Animation Settings

The animationSettings field of the object sample atom is a long integer that specifies a set of
animation settings for an object node. Animation settings specify characteristics of the movie while
it is playing. Use these constants to specify animation settings:

enum QTVRAnimationSettings {
kQTVRObjectAnimateViewFramesOn = (1 << 0),
kQTVRObjectPalindromeViewFramesOn = (1 << 1),
kQTVRObjectStartFirstViewFrameOn = (1 << 2),
kQTVRObjectAnimateViewsOn = (1 << 3),
kQTVRObjectPalindromeViewsOn = (1 << 4),
kQTVRObjectSyncViewToFrameRate = (1 << 5),
kQTVRObjectDontLoopViewFramesOn = (1 << 6),
kQTVRObjectPlayEveryViewFrameOn = (1 << 7)
};


kQTVRObjectAnimateViewFramesOn
If this bit is set, play all frames in the current view state.

kQTVRObjectPalindromeViewFramesOn
If this bit is set, play a back-and-forth animation of the frames of the current view state.

kQTVRObjectStartFirstViewFrameOn
If this bit is set, play the frame animation starting with the first frame in the view (that is, at
the view start time).

kQTVRObjectAnimateViewsOn
If this bit is set, play all views of the current object in the default row of views.

kQTVRObjectPalindromeViewsOn
If this bit is set, play a back-and-forth animation of all views of the current object in the default
row of views.

kQTVRObjectSyncViewToFrameRate
If this bit is set, synchronize the view animation to the frame animation and use the same
options as for frame animation.

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kQTVRObjectDontLoopViewFramesOn
If this bit is set, stop playing the frame animation in the current view at the end.

kQTVRObjectPlayEveryViewFrameOn
If this bit is set, play every view frame regardless of play rate. The play rate is used to adjust
the duration in which a frame appears but no frames are skipped so the rate is not exact.

Control Settings

The controlSettings field of the object sample atom is a long integer that specifies a set of control
settings for an object node. Control settings specify whether the object can wrap during panning and
tilting, as well as other features of the node. The control settings are specified using these bit flags:

enum QTVRControlSettings {
kQTVRObjectWrapPanOn = (1 << 0),
kQTVRObjectWrapTiltOn = (1 << 1),
kQTVRObjectCanZoomOn = (1 << 2),
kQTVRObjectReverseHControlOn = (1 << 3),
kQTVRObjectReverseVControlOn = (1 << 4),
kQTVRObjectSwapHVControlOn = (1 << 5),
kQTVRObjectTranslationOn = (1 << 6)
};

Constant Descriptions

kQTVRObjectWrapPanOn
If this bit is set, enable wrapping during panning. When this control setting is enabled, the
user can wrap around from the current pan constraint maximum value to the pan constraint
minimum value (or vice versa) using the mouse or arrow keys.

kQTVRObjectWrapTiltOn
If this bit is set, enable wrapping during tilting. When this control setting is enabled, the user
can wrap around from the current tilt constraint maximum value to the tilt constraint minimum
value (or vice versa) using the mouse or arrow keys.

kQTVRObjectCanZoomOn
If this bit is set, enable zooming. When this control setting is enabled, the user can change the
current field of view using the zoom-in and zoom-out keys on the keyboard (or using the VR
controller buttons).

kQTVRObjectReverseHControlOn
If this bit is set, reverse the direction of the horizontal control.

kQTVRObjectReverseVControlOn
If this bit is set, reverse the direction of the vertical control.

kQTVRObjectSwapHVControlOn
If this bit is set, exchange the horizontal and vertical controls.

Object Tracks 195

C H A P T E R 3

kQTVRObjectTranslationOn
If this bit is set, enable translation. When this setting is enabled, the user can translate using
the mouse when either the translate key is held down or the controller translation mode button
is toggled on.

Track References for Object Tracks

The track references to an object’s image and hot spot tracks are not handled the same way as track
references to panoramas. The track reference types are the same (kQTVRImageTrackRefType and
kQTVRHotSpotTrackRefAtomType), but the location of the reference indexes is different. There is no
entry in the object sample atom for the track reference indexes. Instead, separate atoms using the
VRTrackRefEntry structure are stored as siblings to the object sample atom. The types of these atoms
are kQTVRImageTrackRefAtomType and kQTVRHotSpotTrackRefAtomType. If either of these atoms
is not present, then the reference index to the corresponding track is assumed to be 1.

Note: The trackResolution field in the VRTrackRefEntry structure is ignored for object tracks.
<8bat>u

The actual views of an object for an object node are contained in an object image track, which is usually
a standard QuickTime video track. (An object image track can also be any type of track that is capable
of displaying an image, such as a QuickTime 3D track.)

As described in Chapter 1 of Programming With QuickTime VR, these views are often captured by
moving a camera around the object in a defined pattern of pan and tilt angles. The views must then
be ordered into an object image array, which is stored as a one-dimensional sequence of frames in
the movie’s video track (see Figure 3-13 (page 196)).

Figure 3-13 The structure of an image track for an object

1,1 1,2 1,3 1,4 ...... 1,m 2,1 2,2 2,3 ..... ..... n,1 n,2 ..... n,m

View duration

For object movies containing frame animation, each animated view in the object image array consists
of the animating frames. It is not necessary that each view in the object image array contain the same
number of frames, but the view duration of all views in the object movie must be the same.

196 Track References for Object Tracks

C H A P T E R 3

For object movies containing alternate view states, alternate view states are stored as separate object
image arrays that immediately follow the preceding view state in the object image track. Each state
does not need to contain the same number of frames. However, the total movie time of each view
state in an object node must be the same.

Movie Media

Movie media is used to encapsulate embedded movies within QuickTime movies. This feature is
available in QuickTime 4.1.

Movie Sample Description
The movie media doesn’t have a unique sample description. It uses the minimum sample description,
which is SampleDescriptionRecord.

Movie Media Sample Format
Each sample in the movie media is a QuickTime atom container. All root level atoms and their contents
are enumerated in the following list. Note that the contents of all atoms are stored in big-endian
format.

kMovieMediaDataReference
This atom contains a data reference type and a data reference. The data reference type is stored
as an OSType at the start of the atom. The data reference is stored following the data reference
type. If the data reference type is URL and the data reference is for a movie on the Apple
website, the contents of the atom would be url http://www.apple.com/foo.mov.

There may be more than one atom of this type. The first atom of this type should have an atom
ID of 1. Additional data references should be numbered sequentially.

kMovieMediaDefaultDataReferenceID
This atom contains a QTAtomID that indicates the ID of the data reference to use when
instantiating the embedded movie for this sample. If this atom is not present, the data reference
with an ID of 1 is used.

kMovieMediaSlaveTime
This atom contains a Boolean that indicates whether or not the TimeBase of the embedded
movie should be slaved to the TimeBase of the parent movie. If the TimeBase is slaved, the
embedded movie’s zero time will correspond to the start time of its movie media sample.
Further, the playback rate of the embedded movie will always be the same as the parent movie’s.
If the TimeBase is not slaved, the embedded movie will default to a rate of 0, and a default
time of whatever default time value it instantiated with (which may not be 0). If the TimeBase
is not slaved, the embedded movie can be played by either including an AutoPlay atom in the
movie media sample or by using a wired action. If this atom is not present, the embedded
movie defaults to not slaved.

Movie Media 197

C H A P T E R 3

kMovieMediaSlaveAudio
This atom contains a Boolean that indicates whether or not the audio properties of the embedded
movie should be slaved to those of the parent movie. When audio is slaved, all audio properties
of the containing track are duplicated in the embedded movie. These properties include sound
volume, balance, bass and treble, and level metering. If this atom is not present, the embedded
movie defaults to not slaved audio.

kMovieMediaSlaveGraphicsMode
This atom contains a Boolean that indicates how the graphics mode of the containing track is
applied to the embedded movie. If the graphics mode is not slaved, then the entire embedded
movie is imaged using its own graphics modes. The result of the drawing of the embedded
movie is composited onto the containing movie using the graphics mode of the containing
track. If the graphics mode is slaved, then the graphics mode of each track in the embedded
movie is ignored and instead the graphics mode of the containing track is used. In this case,
the tracks of the embedded movie composite their drawing directly into the parent movie’s
contents. If this atom is not present, the graphics mode defaults to not slaved. Graphics mode
slaving is useful for compositing semi-transparent media––for example, a PNG with an alpha
channel––on top of other media.

kMovieMediaSlaveTrackDuration
This atom contains a Boolean that indicates how the Movie Media Handler should react when
the duration of the embedded movie is different than the duration of the movie media sample
that it is contained by. When the movie media sample is created, the duration of the embedded
movie may not yet be known. Therefore, the duration of the media sample may not be correct.
In this case, the Movie Media Handler can do one of two things. If this atom is not present or
it contains a value of false, the Movie Media Handler will respect the duration of media sample
that contains the embedded movie. If the embedded movie has a longer duration than the
movie media sample, the embedded movie will be truncated to the duration of the containing
movie media sample. If the embedded movie is shorter, there will be a gap after it is finished
playing. If this atom contains a value of true, the duration of the movie media sample will be
adjusted to match the actual duration of the embedded movie. Because it is not possible to
change an existing media sample, this will cause a new media sample to be added to the movie
and the track’s edit list to be updated to reference the new sample instead of the original sample.

Note: When the duration of the embedded movie’s sample is adjusted, by default no other tracks are
adjusted. This can cause the overall temporal composition to change in unintended ways. To maintain
the complete temporal composition, a higher-level data structure which describes the temporal
relationships between the various tracks must also be included with the movie. u

kMovieMediaAutoPlay
This atom contains a Boolean that indicates whether or not the embedded movie should start
playing immediately after being instantiated. This atom is only used if the TimeBase of the
embedded movie is not slaved to the parent movie (see the kMovieMediaSlaveTime atom
(page 260) (page 197) for more information). If auto play is requested, the movie will be played
at its preferred rate after being instantiated. If this atom is not present, the embedded movie
will not automatically play.

198 Movie Media

C H A P T E R 3

kMovieMediaLoop
This atom contains a UInt8 that indicates how the embedded movie should loop. This atom
is only used if the TimeBase of the embedded movie is not slaved to the parent movie (see the
kMovieMediaSlaveTime atom (page 260) (page 197) for more information). If this atom contains
a 0, or if this atom is not present, the embedded movie will not loop. If this atom contains a
value of 1, the embedded movie loops normally––that is, when it reaches the end it loops back
to the beginning. If this atom contains a value of 2, the embedded movie uses palindromic
looping. All other values are reserved.

kMovieMediaUseMIMEType
This atom contains text (not a C string or a pascal string) that indicates the MIME type of the
movie import component that should be used to instantiate this media. This is useful in cases
where the data reference may not contain MIME type information. If this atom is not present,
the MIME type of the data reference as determined at instantiation time is used. This atom is
intended to allow content creators a method for working around MIME type binding problems.
It should not typically be required, and should not be included in movie media samples by
default.

kMovieMediaTitle
Currently unused. It would contain text indicating the name of the embedded movie.

kMovieMediaAltText
This atom contains text (not a C string or a pascal string) that is displayed to the user when
the embedded movie is being instantiated or if the embedded movie cannot be instantiated.
If this atom is not present, the name of the data reference (typically the file name) is used.

kMovieMediaClipBegin
This atom contains a MovieMediaTimeRecord that indicates the time of the embedded movie
that should be used. The clip begin atom provides a way to specify that a portion of the
beginning of the embedded movie should not be used. If this atom is not present, the beginning
of the embedded movie is not changed. Note that this atom does not change the time at which
the embedded movie begins playing in the parent movie’s time line. If the time specified in
the clip begin atom is greater than the duration of the embedded movie, then the embedded
movie will not play at all.

struct MovieMediaTimeRecord {
wide time;
TimeScale scale;
};

kMovieMediaClipDuration
This atom contains a MovieMediaTimeRecord that indicates the duration of the embedded
movie that should be used. The clip duration atom is applied by removing media from end of
the embedded movie. If the clip duration atom is not present, then no media is removed from
the end of the embedded movie. In situations where the sample contains both a clip duration
and a clip begin atom, the clip begin is applied first. If the clip duration specifies a value that
is larger than the duration of the embedded movie, no change is made to the embedded movie.

Movie Media 199

C H A P T E R 3

kMovieMediaEnableFrameStepping
This atom contains a Boolean that indicates whether or not the embedded movie should be
considered when performing step operations, specifically using the interesting time calls with
the nextTimeStep flag. If this atom is not present or is set to false, the embedded movie is
not included in step calculations. If the atom is set to true, it is included in step calculations.

kMovieMediaBackgroundColor
This atom contains an RGBColor that is used for filling the background when the movie is
being instantiated or when it fails to instantiate.

kMovieMediaRegionAtom
This atom contains a number of child atoms, shown below, which describe how the Movie
Media Handler should resize the embedded movie. If this atom is not present, the Movie Media
Handler resizes the child movie to completely fill the containing track’s box.

kMovieMediaSpatialAdjustment

This atom contains an OSType that indicates how the embedded movie should be scaled to fit
the track box. If this atom is not present, the default value is kMovieMediaFitFill. These
modes are all based on SMIL layout options.

kMovieMediaFitClipIfNecessary

If the media is larger than the track box, it will be clipped; if it is smaller, any additional area
will be transparent.

kMovieMediaFitFill

The media will be scaled to completely fill the track box.

kMovieMediaFitMeet

The media is proportionally scaled so that it is entirely visible in the track box and fills the
largest area possible without changing the aspect ratio.

kMovieMediaFitSlice

The media is scaled proportionally so that the smaller dimension is completely visible.

kMovieMediaFitScroll

Not currently implemented. It currently has the same behavior as
kMovieMediaFitClipIfNecessary. When implemented, it will have the behavior described
in the SMIL specification for a scrolling layout element.

kMovieMediaRectangleAtom
This atom contains four child atoms that define a rectangle. Not all child atoms must be present:
top and left must both appear together, width and height must both appear together. The
dimensions contained in this rectangle are used in place of the track box when applying the
contents of the spatial adjustment atom. If the top and left are not specified, the top and left of
the containing track’s box are used. If the width and height are not specified, the width and
height of the containing track’s box are used. Each child atom contains a UInt32.

kMovieMediaTop kMovieMediaLeft kMovieMediaWidth kMovieMediaHeight

200 Movie Media

C H A P T E R 4

Basic Data Types

This chapter describes a number of common data types that are used in QuickTime files.

Language Code Values

Some elements of a QuickTime file may be associated with a particular spoken language. To indicate
the language associated with a particular object, the QuickTime file format uses language codes from
the Macintosh Script Manager. Table 4-1 (page 201) lists some of the language codes supported by
QuickTime.

Table 4-1 QuickTime language code values

Language Value Language Value

English 0 Georgian 52

French 1 Moldavian 53

German 2 Kirghiz 54

Italian 3 Tajiki 55

Dutch 4 Turkmen 56

Swedish 5 Mongolian 57

Spanish 6 MongolianCyr 58

Danish 7 Pashto 59

Portuguese 8 Kurdish 60

Norwegian 9 Kashmiri 61

Hebrew 10 Sindhi 62

Japanese 11 Tibetan 63

Arabic 12 Nepali 64

Language Code Values 201

C H A P T E R 4
Basic Data Types


Finnish 13 Sanskrit 65

Greek 14 Marathi 66

Icelandic 15 Bengali 67

Maltese 16 Assamese 68

Turkish 17 Gujarati 69

Croatian 18 Punjabi 70

Traditional Chinese 19 Oriya 71

Urdu 20 Malayalam 72

Hindi 21 Kannada 73

Thai 22 Tamil 74

Korean 23 Telugu 75

Lithuanian 24 Sinhalese 76

Polish 25 Burmese 77

Hungarian 26 Khmer 78

Estonian 27 Lao 79

Lettish 28 Vietnamese 80

Latvian 28 Indonesian 81

Saamisk 29 Tagalog 82

Lappish 29 MalayRoman 83

Faeroese 30 MalayArabic 84

Farsi 31 Amharic 85

Tigrinya 86

Russian 32 Galla 87

Simplified Chinese 33 Oromo 87

Flemish 34 Somali 88

Irish 35 Swahili 89

Albanian 36 Ruanda 90

202 Language Code Values

C H A P T E R 4
Basic Data Types


Romanian 37 Rundi 91

Czech 38 Chewa 92

Slovak 39 Malagasy 93

Slovenian 40 Esperanto 94

Yiddish 41 Welsh 128

Serbian 42 Basque 129

Macedonian 43 Catalan 130

Bulgarian 44 Latin 131

Ukrainian 45 Quechua 132

Byelorussian 46 Guarani 133

Uzbek 47 Aymara 134

Kazakh 48 Tatar 135

Azerbaijani 49 Uighur 136

AzerbaijanAr 50 Dzongkha 137

Armenian 51 JavaneseRom 138

Calendar Date and Time Values

QuickTime movies store date and time information in Macintosh date format: a 32-bit value indicating
the number of seconds that have passed since midnight January 1, 1904.

Matrices

QuickTime files use matrices to describe spatial information about many objects, such as tracks within
a movie.

A transformation matrix defines how to map points from one coordinate space into another coordinate
space. By modifiying the contents of a transformation matrix, you can perform several standard
graphics display operations, including translation, rotation, and scaling. The matrix used to accomplish
two-dimensional transformations is described mathematically by a 3-by-3 matrix.

Calendar Date and Time Values 203

C H A P T E R 4
Basic Data Types

All values in the matrix are 32-bit fixed-point numbers divided as 16.16, except for the {u, v, w} column,
which contains 32-bit fixed-point numbers divided as 2.30. Figure 4-1 (page 204) depicts how QuickTime
uses matrices to transform displayed objects.

Figure 4-1 How display matrices are used in QuickTime

a b u
x y 1 x c d v = x' y' 1

tx ty w

Figure 4-2 Applying the transform

Movie atom

Atom size
Type = 'moov'

Movie header atom 'mvhd'‡


One or more track atoms 'trak'


Color table atom 'ctab'

‡ Required atom

Graphics Modes

QuickTime files use graphics modes to describe how one video or graphics layer should be combined
with the layers beneath it. Graphics modes are also known as transfer modes. Some graphics modes
require a color to be specified for certain operations, such as blending to determine the blend level.
QuickTime uses the graphics modes defined by Apple’s QuickDraw.

The most common graphics modes are and ditherCopy, which simply indicate that the image should
not blend with the image behind it, but overwrite it. QuickTime also defines several additional graphics
modes.

Table 4-2 (page 205) lists the additional graphics modes supported by QuickTime.

204 Graphics Modes

C H A P T E R 4
Basic Data Types

Table 4-2 QuickTime graphics modes

Uses
Mode Code Description
opcolor

Copy 0x0 Copy the source image over the
destination.

Dither copy 0x40 Dither the image (if needed), otherwise
do a copy.

Blend yes 0x20 Replaces destination pixel with a blend
of the source and destination pixel
colors, with the proportion for each
channel controlled by that channel in
the opcolor.

Transparent yes 0x24 Replaces the destination pixel with the
source pixel if the source pixel isn't
equal to the opcolor.

Straight alpha 0x100 Replaces the destination pixel with a
blend of the source and destination
pixels, with the proportion controlled
by the alpha channel.

Premul white 0x101 Pre-multiplied with white means that
alpha the color components of each pixel
have already been blended with a
white pixel, based on their alpha
channel value. Effectively, this means
that the image has already been
combined with a white background.
First, remove the white from each pixel
and then blend the image with the
actual background pixels.

Premul black 0x102 Pre-multipled with black is the same
alpha as pre-multipled with white, except the
background color that the image has
been blended with is black instead of
white.

Straight alpha yes 0x104 Similar to straight alpha, but the alpha
blend value used for each channel is the
combination of the alpha channel and
that channel in the opcolor.

Composition 0x103 (Tracks only) The track is drawn
(dither copy) offscreen, and then composed onto the
screen using dither copy

Graphics Modes 205

C H A P T E R 4
Basic Data Types

RGB Colors

Many atoms in the QuickTime file format contain RGB color values. These are usually stored as three
consecutive unsigned 16-bit integers in the following order: red, green, blue.

Balance

Balance values are represented as 16-bit, fixed-point numbers that range from -1.0 to +1.0. The
high-order 8 bits contain the integer portion of the value; the low-order 8 bits contain the fractional
part. Negative values weight the balance toward the left speaker; positive values emphasize the right
channel. Setting the balance to 0 corresponds to a neutral setting.

206 RGB Colors

C H A P T E R 5

Some Useful Examples and Scenarios

This chapter contains a number of examples that can help you pull together all of the material in this
book by examining the atom structure that results from a number of different scenarios.

The chapter is divided into the following topics:

■ “Creating, Copying, and Disposing of Atom Containers” (page 208) discusses the various ways
you can work with atom containers, along with illustrations and sample code that show usage.
■ “Creating an Effect Description” (page 215) discusses how you create an effect description by
creating an atom container, inserting a QT atom that specifies the effect, and inserting a set of QT
atoms that set its parameters.
■ “Creating Movies With Modifier Tracks” (page 220) provides sample code showing you how to
create a movie with modifier tracks.
■ “Authoring Movies With External Movie Targets” (page 221) discusses how to author movies with
external targets, using two new target atoms introduced in QuickTime 4.
■ “Adding Wired Actions To a Flash Track” (page 222) explains the steps you need to follow in order
to add wired actions to a Macromedia Flash track.
■ “Creating Video Tracks at 30 Frames-per-Second” (page 225) discusses creating 30 fps video.
■ “Creating Video Tracks at 29.97 Frames-per-Second” (page 225) describes creating 29.97 fps video.
■ “Creating Audio Tracks at 44.1 Khz” (page 226) provides an example of creating an audio track.
■ “Creating a Timecode Track for 29.97 FPS Video” (page 226) presents a timecode track example.
■ “Playing With Edit Lists” (page 230) discusses how to interpret edit list data.
■ “Interleaving Movie Data” (page 232) shows how a movie’s tracks are interleaved in the movie
data file.
■ “Referencing Two Data Files With a Single Track” (page 233) shows how track data may reside in
more than one file.
■ “Getting the Name of a QuickTime VR Node” (page 234) discusses how you can use standard
QuickTime atom container functions to retrieve the information in a QuickTime VR node header
atom.
■ “Adding Custom Atoms in a QuickTime VR Movie” (page 236) describes how to add custom atoms
to either the QuickTime VR world or node information atom containers.
■ “Adding Atom Containers in a QuickTime VR Movie” (page 237) shows the code you would use
to add VR world and node information atom containers to a QTVR track.

207

C H A P T E R 5

■ “Optimizing QuickTime VR Movies for Web Playback” (page 238) describes how to use the QTVR
Flattener, a movie export component that converts an existing QuickTime VR single node movie
into a new movie that is optimized for viewing on the Web.

Creating, Copying, and Disposing of Atom Containers

Before you can add atoms to an atom container, you must first create the container by calling
QTNewAtomContainer. The code sample shown in Listing 5-1 (page 208) calls QTNewAtomContainer
to create an atom container.

Listing 5-1 Creating a new atom container

QTAtomContainer spriteData;
OSErr err
// create an atom container to hold a sprite’s data
err=QTNewAtomContainer (&spriteData);

When you have finished using an atom container, you should dispose of it by calling the
QTDisposeAtomContainer function. The sample code shown in Listing 5-2 (page 208) calls
QTDisposeAtomContainer to dispose of the spriteData atom container.

Listing 5-2 Disposing of an atom container

if (spriteData)
QTDisposeAtomContainer (spriteData);

Creating New Atoms
You can use the QTInsertChild function to create new atoms and insert them in a QT atom container.
The QTInsertChild function creates a new child atom for a parent atom. The caller specifies an atom
type and atom ID for the new atom. If you specify a value of 0 for the atom ID, QTInsertChild assigns
a unique ID to the atom.

QTInsertChild inserts the atom in the parent’s child list at the index specified by the index parameter;
any existing atoms at the same index or greater are moved toward the end of the child list. If you
specify a value of 0 for the index parameter, QTInsertChild inserts the atom at the end of the child
list.

The code sample in Listing 5-3 (page 208) creates a new QT atom container and calls QTInsertChild
to add an atom. The resulting QT atom container is shown in Figure 5-1 (page 209). The offset value
10 is returned in the firstAtom parameter.

Listing 5-3 Creating a new QT atom container and calling QTInsertChild to add an atom.

QTAtom firstAtom;
QTAtomContainer container;
OSErr err
err = QTNewAtomContainer (&container);
if (!err)
err = QTInsertChild (container, kParentAtomIsContainer, 'abcd',

208 Creating, Copying, and Disposing of Atom Containers

C H A P T E R 5

1000, 1, 0, nil, &firstAtom);

Figure 5-1 QT atom container after inserting an atom

QT atom
container

Index = 1
'abcd' Offset = 10
1000

The following code sample calls QTInsertChild to create a second child atom. Because a value of 1
is specified for the index parameter, the second atom is inserted in front of the first atom in the child
list; the index of the first atom is changed to 2. The resulting QT atom container is shown in Figure
5-2 (page 209).

QTAtom secondAtom;

FailOSErr (QTInsertChild (container, kParentAtomIsContainer, 'abcd',
2000, 1, 0, nil, &secondAtom));

Figure 5-2 QT atom container after inserting a second atom

QT atom
container

Index = 1 Index = 2
Offset = 10 'abcd' 'abcd' Offset = 20
2000 1000

You can call the QTFindChildByID function to retrieve the changed offset of the first atom that was
inserted, as shown in the following example. In this example, the QTFindChildByID function returns
an offset of 20.

firstAtom = QTFindChildByID (container, kParentAtomIsContainer, 'abcd',
1000, nil);

Listing 5-4 (page 209) shows how the QTInsertChild function inserts a leaf atom into the atom container
sprite. The new leaf atom contains a sprite image index as its data.

Listing 5-4 Inserting a child atom

if ((propertyAtom = QTFindChildByIndex (sprite, kParentAtomIsContainer,
kSpritePropertyImageIndex, 1, nil)) == 0)

FailOSErr (QTInsertChild (sprite, kParentAtomIsContainer,
kSpritePropertyImageIndex, 1, 1, sizeof(short),&imageIndex,


C H A P T E R 5

nil));

Copying Existing Atoms
QuickTime provides several functions for copying existing atoms within an atom container. The
QTInsertChildren function inserts a container of atoms as children of a parent atom in another atom
container. Figure 5-3 (page 210) shows two example QT atom containers, A and B.

Figure 5-3 Two QT atom containers, A and B

QT atom QT atom
container A container B

Index= 1 Index = 1 'hijk' Index = 2
Offset= 10 'abcd' Offset = 10 'defg' Offset = 20
1000 900 2000

Data

The following code sample calls QTFindChildByID to retrieve the offset of the atom in container A.
Then, the code sample calls the QTInsertChildren function to insert the atoms in container B as
children of the atom in container A. Figure 5-4 (page 211) shows what container A looks like after the
atoms from container B have been inserted.

QTAtom targetAtom;

targetAtom = QTFindChildByID (containerA, kParentAtomIsContainer, 'abcd',
1000, nil);

FailOSErr (QTInsertChildren (containerA, targetAtom, containerB));


C H A P T E R 5

Figure 5-4 QT atom container after child atoms have been inserted

QT atom
container A

Index = 1
'abcd' Offset = 10
1000

Index = 1 Index = 2
'defg' 'hijk'
Offset = 20 Offset = 30
900 2000

Data

In Listing 5-5 (page 211), the QTInsertChild function inserts a parent atom into the atom container
theSample. Then, the code calls QTInsertChildren to insert the container theSprite into the container
theSample. The parent atom is newSpriteAtom.

Listing 5-5 Inserting a container into another container

FailOSErr (QTInsertChild (theSample, kParentAtomIsContainer,
kSpriteAtomType, spriteID, 0, 0, nil, &newSpriteAtom));

FailOSErr (QTInsertChildren (theSample, newSpriteAtom, theSprite));

QuickTime provides three other functions you can use to manipulate atoms in an atom container.
The QTReplaceAtom function replaces an atom and its children with a different atom and its children.
You can call the QTSwapAtoms function to swap the contents of two atoms in an atom container; after
swapping, the ID and index of each atom remains the same. The QTCopyAtom function copies an atom
and its children to a new atom container.

Retrieving Atoms From an Atom Container
QuickTime provides functions you can use to retrieve information about the types of a parent atom’s
children, to search for a specific atom, and to retrieve a leaf atom’s data.

You can use the QTCountChildrenOfType and QTGetNextChildType functions to retrieve information
about the types of an atom’s children. The QTCountChildrenOfType function returns the number of
children of a given atom type for a parent atom. The QTGetNextChildType function returns the next
atom type in the child list of a parent atom.

You can use the QTFindChildByIndex, QTFindChildByID, and QTNextChildAnyType functions to
retrieve an atom. You call the QTFindChildByIndex function to search for and retrieve a parent atom’s
child by its type and index within that type.


C H A P T E R 5

Listing 5-6 (page 212) shows the sample code function SetSpriteData, which updates an atom container
that describes a sprite. (For more information about sprites and the Sprite Toolbox, refer to the book
Programming With Wired Movies and Sprite Animation, available at
http://developer.apple.com/documentation/Quicktime/RM/PDF.htm.) For each property of the
sprite that needs to be updated, SetSpriteData calls QTFindChildByIndex to retrieve the appropriate
atom from the atom container. If the atom is found, SetSpriteData calls QTSetAtomData to replace
the atom’s data with the new value of the property. If the atom is not found, SetSpriteData calls
QTInsertChild to add a new atom for the property.

Listing 5-6 Finding a child atom by index

OSErr SetSpriteData (QTAtomContainer sprite, Point *location,
short *visible, short *layer, short *imageIndex)
{
OSErr err = noErr;
QTAtom propertyAtom;

// if the sprite’s visible property has a new value
if (visible)
{
// retrieve the atom for the visible property --
// if none exists, insert one
if ((propertyAtom = QTFindChildByIndex (sprite,
kParentAtomIsContainer, kSpritePropertyVisible, 1,
nil)) == 0)
kSpritePropertyVisible, 1, 1, sizeof(short), visible,
nil))

// if an atom does exist, update its data
else
FailOSErr (QTSetAtomData (sprite, propertyAtom,
sizeof(short), visible));
}

// ...
// handle other sprite properties
// ...
}

You can call the QTFindChildByID function to search for and retrieve a parent atom’s child by its
type and ID. The sample code function AddSpriteToSample, shown in Listing 5-7 (page 212), adds a
sprite, represented by an atom container, to a key sample, represented by another atom container.
AddSpriteToSample calls QTFindChildByID to determine whether the atom container theSample
contains an atom of type kSpriteAtomType with the ID spriteID. If not, AddSpriteToSample calls
QTInsertChild to insert an atom with that type and ID. A value of 0 is passed for the index parameter
to indicate that the atom should be inserted at the end of the child list. A value of 0 is passed for the
dataSize parameter to indicate that the atom does not have any data. Then, AddSpriteToSample
calls QTInsertChildren to insert the atoms in the container theSprite as children of the new atom.
FailIf and FailOSErr are macros that exit the current function when an error occurs.

Listing 5-7 Finding a child atom by ID

OSErr AddSpriteToSample (QTAtomContainer theSample,
QTAtomContainer theSprite, short spriteID)
{


C H A P T E R 5

OSErr err = noErr;
QTAtom newSpriteAtom;

FailIf (QTFindChildByID (theSample, kParentAtomIsContainer,
kSpriteAtomType, spriteID, nil), paramErr);

FailOSErr (QTInsertChild (theSample, kParentAtomIsContainer,
kSpriteAtomType, spriteID, 0, 0, nil, &newSpriteAtom));
FailOSErr (QTInsertChildren (theSample, newSpriteAtom, theSprite));
}

Once you have retrieved a child atom, you can call QTNextChildAnyType function to retrieve
subsequent children of a parent atom. QTNextChildAnyType returns an offset to the next atom of any
type in a parent atom’s child list. This function is useful for iterating through a parent atom’s children
quickly.

QuickTime also provides functions for retrieving an atom’s type, ID, and data. You can call
QTGetAtomTypeAndID function to retrieve an atom’s type and ID. You can access an atom’s data in
one of three ways.

■ To copy an atom’s data to a handle, you can use the QTCopyAtomDataToHandle function.
■ To copy an atom’s data to a pointer, you can use the QTCopyAtomDataToPtr function.
■ To access an atom’s data directly, you should lock the atom container in memory by calling
QTLockContainer. Once the container is locked, you can call QTGetAtomDataPtr to retrieve a
pointer to an atom’s data. When you have finished accessing the atom’s data, you should call the
QTUnlockContainer function to unlock the container in memory.

Modifying Atoms
QuickTime provides functions that you can call to modify attributes or data associated with an atom
in an atom container. To modify an atom’s ID, you call the function QTSetAtomID.

You use the QTSetAtomData function to update the data associated with a leaf atom in an atom
container. The QTSetAtomData function replaces a leaf atom’s data with new data. The code sample
in Listing 5-8 (page 213) calls

QTFindChildByIndex to determine whether an atom container contains a sprite’s visible property.
If so, the sample calls QTSetAtomData to replace the atom’s data with a new visible property.

Listing 5-8 Modifying an atom’s data

QTAtom propertyAtom;

// if the atom isn’t in the container, add it
if ((propertyAtom = QTFindChildByIndex (sprite, kParentAtomIsContainer,
kSpritePropertyVisible, 1, nil)) == 0)
kSpritePropertyVisible, 1, 0, sizeof(short), visible, nil))

// if the atom is in the container, replace its data
else
FailOSErr (QTSetAtomData (sprite, propertyAtom, sizeof(short),
visible));


C H A P T E R 5

Removing Atoms From an Atom Container
To remove atoms from an atom container, you can use the QTRemoveAtom and QTRemoveChildren
functions. The QTRemoveAtom function removes an atom and its children, if any, from a container.
The QTRemoveChildren function removes an atom’s children from a container, but does not remove
the atom itself. You can also use QTRemoveChildren to remove all the atoms in an atom container.
To do so, you should pass the constant kParentAtomIsContainer for the atom parameter.

The code sample shown in Listing 5-9 (page 214) adds override samples to a sprite track to animate
the sprites in the sprite track. The sample and spriteData variables are atom containers. The
spriteData atom container contains atoms that describe a single sprite. The sample atom container
contains atoms that describes an override sample.

Each iteration of the for loop calls QTRemoveChildren to remove all atoms from both the sample and
the spriteData containers. The sample code updates the index of the image to be used for the sprite
and the sprite’s location and calls SetSpriteData ( Listing 5-6 (page 212)), which adds the appropriate
atoms to the spriteData atom container. Then, the sample code calls AddSpriteToSample ( Listing
5-7 (page 212)) to add the spriteData atom container to the sample atom container. Finally, when all
the sprites have been updated, the sample code calls AddSpriteSampleToMedia to add the override
sample to the sprite track.

Listing 5-9 Removing atoms from a container

QTAtomContainer sample, spriteData;

// ...
// add the sprite key sample
// ...

// add override samples to make the sprites spin and move
for (i = 1; i <= kNumOverrideSamples; i++)
{
QTRemoveChildren (sample, kParentAtomIsContainer);
QTRemoveChildren (spriteData, kParentAtomIsContainer);

// ...
// update the sprite:
// - update the imageIndex
// - update the location
// ...

// add atoms to spriteData atom container
SetSpriteData (spriteData, &location, nil, nil, &imageIndex);

// add the spriteData atom container to sample
err = AddSpriteToSample (sample, spriteData, 2);

// ...
// update other sprites
// ...

// add the sample to the media
err = AddSpriteSampleToMedia (newMedia, sample,
kSpriteMediaFrameDuration, false);
}


C H A P T E R 5

Creating an Effect Description

An effect description tells QuickTime which effect to execute and contains the parameters that control
how the effect behaves at runtime. You create an effect description by creating an atom container,
inserting a QT atom that specifies the effect, and inserting a set of QT atoms that set its parameters.

There are support functions you can call to assist you in this process.
QTCreateStandardParameterDialog returns a complete effect description that you can use, including
user-selected settings; you only need to add kEffectSourceName atoms to the description for effects
that require sources. At a lower level, QTGetEffectsList returns a list of the available effects and
ImageCodecGetParameterList will return a description of the parameters for an effect, including
the default value for each parameter in the form of a QT atom that can be inserted directly into an
effect description.

Structure of an Effect Description
An effect description is the sole media sample for an effect track. An effect description is implemented
as a QTAtomContainer structure, the general QuickTime structure for holding a set of QuickTime
atoms. All effect descriptions must contain the set of required atoms, which specify attributes such
as which effect component to use. In addition, effect descriptions can contain a variable number of
parameter atoms, which hold the values of the parameters for the effect.

Each atom contains either data or a set of child atoms. If a parameter atom contains data, the data is
the value of the parameter, and this value remains constant while the effect executes. If a parameter
atom contains a set of child atoms, they typically contain a tween entry so the value of the parameter
will be interpolated for the duration of the effect.

You assemble an effect description by adding the appropriate set of atoms to a QTAtomContainer
structure.

You can find out what the appropriate atoms are by making an ImageCodecGetParameterList call
to the effect component. This fills an atom container with a set of parameter description atoms. These
atoms contain descriptions of the effect parameters, such as each parameter’s atom type, data range,
default value, and so on. The default value in each description atom is itself a QTAtom that can be
inserted directly into your effect description.

You can modify the data in the parameter atoms directly, or let the user set them by calling
QTCreateStandardParameterDialog, which returns a complete effect description (you need to add
kEffectSourceName atoms for effects that require sources).

You then add the effect description to the media of the effect track.

Required Atoms of an Effects Description
There are several required atoms that an effect description must contain. The first is the
kParameterWhatName atom. The kParameterWhatName atom contains the name of the effect. This
specifies which of the available effects to use.


C H A P T E R 5

The code snippet shown in Listing 5-10 (page 216) adds a kParameterWhatName atom to the atom
container effectDescription. The constant kCrossFadeTransitionType contains the name of the
cross-fade effect.

Listing 5-10 Adding a kParameterWhatName atom to the atom container effectDescription

effectCode = kCrossFadeTransitionType;
QTInsertChild(effectDescription, kParentAtomIsContainer,
kParameterWhatName, kParameterWhatID, 0,
sizeof(effectCode), &effectCode, nil);

In addition to the kParameterWhatName atom, the effect description for an effect that uses sources
must contain one or more kEffectSourceName atoms. Each of these atoms contains the name of one
of the effect’s sources. An input map is used to map these names to the actual tracks of the movie that
are the sources. “Creating an Input Map” (page 217) describes how to create the input map.

Parameter Atoms of an Effects Description
In addition to the required atoms, the effects description contains a variable number of parameter
atoms. The number and types of parameter atoms vary from effect to effect. For example, the cross
fade effect has only one parameter, while the general convolution filter effect has nine. Some effects
have no parameters at all, and do not require any parameter atoms.

You can obtain the list of parameter atoms for a given effect by calling the effect component using
ImageCodecGetParameterList. The parameter description atoms it returns include default settings
for each parameter in the form of parameter atoms that you can insert into your effect description.

The QTInsertChild function is used to add these parameters to the effect description, as seen in the
code example in Listing 5-10 (page 216).

Consider, for instance, the push effect. Its effect description contains a kParameterWhatName atom,
two kEffectSourceName atoms, and two parameter atoms, one of which is a tween.

The kParameterWhatName atom specifies that this is a 'push' effect.

The two kEffectSourceName atoms specify the two sources that this effect will use, in this case 'srcA'
and 'srcB'. The names correspond to entries in the effect track’s input map.

The 'pcnt' parameter atom defines which frames of the effect are shown. This parameter contains
a tween entry, so that the value of this parameter is interpolated as the effect runs . The interpolation
of the 'pcnt' parameter causes consecutive frames of the effect to be rendered, creating the push
effect.

The 'from' parameter determines the direction of the push. This parameter is set from an enumeration
list, with 2 being defined as the bottom of the screen.

In this example, the source 'srcB' will push in from the bottom, covering the source 'srcA'.

The 'pcnt' parameter is normally tweened from 0 to 100, so that the effect renders completely, from
0 to 100 percent. In this example, the 'pcnt' parameter is tweened from 25 to 75, so the effect will
start 25% of the way through (with 'srcB' already partly on screen) and finish 75% of the way through
(with part of 'srcA' still visible).

Figure 5-5 (page 217) shows the set of atoms that must be added to the entry description.

216 Creating an Effect Description

C H A P T E R 5

Figure 5-5 An example effect description for the Push effect

Required atoms Byte

Use the effect component with 1
kParameterWhatName
the name 'push'
'push'

The first source is 'srcA'
kEffectSourceName 1
which is the name of a source
defined in the input map
'srcA'

The second source is 'srcB' kEffectSourceName 2
from the input map.
'srcB'

Parameter atoms

The percentage value, which 'pcnt' 1
is tweened for 25% to 75%
'srcB'
kTweenType 1

kParamTypeDataFixed

kTweenData 1

0.25

0.75

The direction from which the
'from' 1
second source pushes the
first. The value 2 indicates
it pushes in from below. 2

An important property of effect parameters is that most can be tweened (and some must be tweened).
Tweening is QuickTime’s general purpose interpolation mechanism (see “Tween Media” (page 136)
for more information). For many parameters, it is desirable to allow the value of the parameter to
change as the effect executes. In the example shown in Figure 5-5 (page 217), the 'pcnt' parameter
must be a tween. This parameter controls which frame of the effect is rendered at any given time, so
it must change for the effect to progress. The 'from' parameter is not a tween in the example above,
but it could be if we wanted the direction of the push to change during the course of the effect.

Creating an Input Map
The input map is another QTAtomContainer that you attach to the effects track. It describes the sources
used in the effect and gives a name to each source. This name is used to refer to the source in the effect
description.


C H A P T E R 5

An input map works in concert with track reference atoms in the source tracks. A track reference
atom of type kTrackModifierReference is added to each source track, which causes that source
track’s output to be redirected to the effects track. An input map is added to the effects track to identify
the source tracks and give a name to each source, such as 'srcA' and 'srcB'. The effect can then
refer to the sources by name, specifying that 'srcB' should slide in over 'srcA', for example.

Structure of an Input Map

The input map contains a set of atoms that refer to the tracks used as sources for the effect. Each
source track is represented by one track reference atom of type kTrackModifierInput.

Each modifier input atom contains two children, one of type kEffectDataSourceType, and one of
type kTrackModifierType, which hold the name and type of the source.

The name of the source is a unique identifier that you create, which is used in the effect description
to reference the track. Any four-character name is valid, as long as it is unique in the set of source
names.

Important: Apple recommends you adopt the standard naming convention 'srcX', where X is a
letter of the alphabet. Thus, your first source would be named 'srcA', the second 'srcB', and so
forth. This convention is used here in this chapter. s

The child atom of type kTrackModifierType indicates the type of the track being referenced. For a
video track the type is VideoMediaType, for a sprite track it is SpriteMediaType, and so forth. Video
tracks are the most common track type used as sources for effects. Only tracks that have a visible
output, such as video and sprite tracks, can be used as sources for an effect. This means, for example,
that sound tracks cannot be sources for an effect.

Figure 5-6 (page 219) shows a completed input map that references two sources. The first source is a
video track and is called 'srcA'. The second source, also a video track, is called 'srcB'.

You refer to a kTrackModifierInput atom by its index number, which is returned by the
AddTrackReference function when you create the atom.

218 Creating an Effect Description

C H A P T E R 5

Figure 5-6 An example input map referencing two sources

Byte

The first reference atom. The ID kTrackModifierInput 5
number is the number returned by
AddTrackReference
'srcB'
kTrackModifierType 1
It is a video track.
VideoMediaType

The name used in the effect kEffectDataSourceType
description is 'scrA' 1

'scrA'

The second reference atom. The ID
number is the number returned
kTrackModifierInput 2
by AddTrackReference
'srcB'
It is a video track. kTrackModifierType 1

VideoMediaType

The name used in the effect
description is 'scrB' kEffectDataSourceType 1

'srcB'

Building Input Maps

The first step in creating an input map is to create a new QTAtomContainer to hold the map. You use
the standard QuickTime container creation function:

QTNewAtomContainer(&inputMap);

For each source you are creating, you need to call the AddTrackReference function. The track IDs of
the effects track and the source track are passed as parameters to AddTrackReference, which creates
an atom of type kTrackModifierReference and returns an index number. You use this index as the
ID of the atom when you need to refer to it. You then insert the reference into the input map as an
atom of type kTrackModifierInput.

The code in Listing 5-11 (page 219) creates a reference to the track firstSourceTrack, and adds it to
the input map.

Listing 5-11 Adding an input reference atom to an input map

AddTrackReference(theEffectsTrack, firstSourceTrack,
kTrackModifierReference, &referenceIndex);

QTInsertChild(inputMap, kParentAtomIsContainer,
kTrackModifierInput, referenceIndex, 0, 0, nil, &inputAtom);

The QTInsertChild function returns the offset of the new modifier input atom in the inputAtom
parameter.

You now need to add the name and type of the source track to the modifier input atom. Again, calling
the QTInsertChild function does this, as shown in the following code snippet:

inputType = VideoMediaType;
QTInsertChild(inputMap, inputAtom,


C H A P T E R 5

kTrackModifierType, 1, 0, sizeof(inputType), &inputType,
nil);

aType = 'srcA';
QTInsertChild(inputMap, inputAtom, kEffectDataSourceType, 1, 0,
sizeof(aType), &aType, nil);

This process is repeated for each source for the effect.

Creating Movies With Modifier Tracks

QuickTime 2.1 added additional functionality for media handlers. By way of modifier tracks, a media
handler can send its data to another media handler rather than presenting its media directly. See
“Modifier Tracks” (page 145) for a complete discussion of this feature.

To create a movie with modifier tracks, first you create a movie with all the desired tracks, then you
create the modifier track. To link the modifier track to the track that it modifies, you use the
AddTrackReference function as shown in Listing 5-12 (page 220).

Listing 5-12 Linking a modifier track to the track it modifies

long addedIndex;
AddTrackReference(aVideoTrack, aModifierTrack,
kTrackModifierReference, &addedIndex);

The reference doesn’t completely describe the modifier track’s relationship to the track it modifies.
Instead, the reference simply tells the modifier track to send its data to the specified track. The receiving
track doesn’t “know” what it should do with that data. A single track may also be receiving data from
more than one modifier track.

To describe how each modifier input should be used, each track’s media also has an input map. The
media’s input map describes how the data being sent to each input of a track should be interpreted
by the receiving track. After creating the reference, it is necessary to update the receiving track’s
media input map. When AddTrackReference is called, it returns the index of the reference added.
That index is the index of the input that needs to be described in the media input map. If the modifier
track created above contains regions to change the shape of the video track, the code shown in Listing
5-13 (page 220) updates the input map appropriately.

Listing 5-13 Updating the input map

QTAtomContainer inputMap;
QTAtom inputAtom;
OSType inputType;

Media aVideoMedia = GetTrackMedia(aVideoTrack);
GetMediaInputMap (aVideoMedia, &inputMap);

QTInsertChild(inputMap, kParentAtomIsContainer, kTrackModifierInput,
addedIndex, 0,0, nil, &inputAtom);

inputType = kTrackModifierTypeClip;
QTInsertChild (inputMap, inputAtom, kTrackModifierType, 1, 0,

220 Creating Movies With Modifier Tracks

C H A P T E R 5

sizeof(inputType), &inputType, nil);

SetMediaInputMap(aVideoMedia, inputMap);
QTDisposeAtomContainer(inputMap);

The media input map allows you to store additional information for each input. In the preceding
example, only the type of the input is specified. In other types of references, you may need to specify
additional data.

When a modifier track is playing an empty track edit, or is disabled or deleted, all receiving tracks
are notified that the track input is inactive. When an input becomes inactive, it is reset to its default
value. For example, if a track is receiving data from a clip modifier track and that input becomes
inactive, the shape of the track reverts to the shape it would have if there were no clip modifier track.

Authoring Movies With External Movie Targets

QuickTime 4 enables you to author movies with external movie targets. To specify an action that
targets an element of an external movie, you must identify the external movie by either its name or
its ID. Two new target atom types have been introduced for this purpose; these atoms are used in
addition to the existing target atoms, which you may use to specify that the element is a particular
track or object within a track, such as a sprite.

Note: A movie ID may be specified by an expression. u

The additional target atoms provided in QuickTime 4:

<kActionTarget>

<kTargetMovieName>
[Pstring MovieName]
OR
<kTargetMovieID>
[long MovieID]
OR

To tag a movie with a name or ID, you add a user data item of type 'plug' to the movie’s user data.
The index of the user data does not matter. The data specifies the name or ID.

You add a user data item of type 'plug' to the movie’s user data with its data set to

"Movieid=MovieName"

where MovieName is the name of the movie.

You add a user data item of type 'plug' to the movie’s user data with its data set to

"Movieid=MovieID"

where the ID is a signed long integer.

Authoring Movies With External Movie Targets 221

C H A P T E R 5

The QuickTime plug-in additionally supports EMBED tag parameters, which allow you to override
a movie’s name or ID within an HTML page.

Target Atoms for Embedded Movies
QuickTime 4.1 introduced target atoms to accommodate the addition of embedded movies. These
target atoms allow for paths to be specified in a hierarchical movie tree.

Target movies may be an external movie, the default movie, or any movie embedded within another
movie. Targets are specified by using a movie path that may include parent and child movie
relationships, and may additionally include track and track object target atoms as needed.

By using embedded kActionTarget atoms along with parent and child movie target atoms, you can
build up paths for movie targets. Note that QuickTime looks for these embedded kActionTarget
atoms only when evaluating a movie target, and any movie target type may contain a sibling
kActionTarget atom.

Paths begin from the current movie, which is the movie containing the object that is handling an
event. You may go up the tree using a kTargetParentMovie atom, or down the tree using one of five
new child movie atoms. You may use a kTargetRootMovie atom as a shortcut to get to the top of the
tree containing an embedded movie and may use the movieByName and movieByID atoms to specify
a root external movie.

The target atoms are

■ kTargetRootMovie (leaf atom, no data). This is the root movie containing the action handler.

■ kTargetParentMovie (leaf atom, no data). This is the parent movie.

Note that there are five ways to specify an embedded child movie. Three of them specify movie track
properties. Two specify properties of the currently loaded movie in a movie track.

■ kTargetChildMovieTrackName. A child movie track specified by track name.

■ kTargetChildMovieTrackID. A child movie track specified by track ID.

■ kTargetChildMovieTrackIndex. A child movie track specified by track index.

■ kTargetChildMovieMovieName. A child movie specified by the currently loaded movie’s movie
name. The child movie must contain movieName user data with the specified name.
■ kTargetChildMovieMovieID. A child movie specified by the currently loaded movie’s movie ID.
The child movie must contain movieID user data with the specified ID.

Adding Wired Actions To a Flash Track

This section explains the steps you need to follow in order to add wired actions to a Macromedia
Flash track. The Flash media handler was introduced in QuickTime 4 to enable a SWF 3.0 file to be
treated as a track within a QuickTime movie. See “Flash Media” (page 135) for more information about
the Flash media handler.

222 Adding Wired Actions To a Flash Track

C H A P T E R 5

Sample code (AddFlashActions) is provided on the QuickTime SDK, as well as on the QuickTime
developer website, that lets you add wired actions to a Flash track.

Note: For more detailed information about working with Flash, you can download the Macromedia
SWF File Format Specification at http://www.macromedia.com/software/flash/open/spec/, along
with the SWF File Parser code also at the Macromedia website. u

Extending the SWF Format
QuickTime 4 extends the SWF file format to allow the execution of any of its wired actions, in addition
to the much smaller set of Flash actions. For example, you may use a SWF file as a user interface
element in a QuickTime movie, controlling properties of the movie and other tracks. QuickTime also
allows SWF files to be compressed using the zlib data compressor. This can significantly lower the
bandwidth required when downloading a SWF file when it is in a QuickTime movie.

By using wired actions within a Flash track, compressing your Flash tracks, and combining Flash
tracks with other types of QuickTime media, you can create compact and sophisticated multimedia
content.

The SWF File Format Specification consists of a header followed by a series of tagged data blocks.
The types of tagged data blocks you need to use are the DefineButton2 and DoAction. The
DefineButton2 block allows Flash actions to be associated with a mouse state transition. DoAction
allows actions to be executed when the tag is encountered. These are analogous to mouse-related QT
event handlers and the frame loaded event in wired movies.

Flash actions are stored in an action record. Each Flash action has its own tag, such as ActionPlay
and ActionNextFrame. QuickTime defines one new tag: QuickTimeActions, which is 0xAA. The data
for the QuickTime actions tag is simply a QT atom container with the QuickTime wired actions to
execute in it.

There are also fields you need to change in order to add wired actions to a SWF file. Additionally,
there is one tag missing from the SWF file format that is described below.

What You Need to Modify

For defineButton2, you need to modify or add the following fields: file length, action records offset,
the action offset, the condition, the record header size portion, and add action record.

File Length

A 32-bit field in the SWF file header.

RecordHeader for the defineButton2

RecordHeader contains the tag ID and length. You need to update the length. Note that there are
short and long formats for record headers, depending on the size of the record. The tag ID for
defineButton2 is 34.

Adding Wired Actions To a Flash Track 223

C H A P T E R 5

ActionRecordsOffset

The action records offset, a 16-bit field, is missing from the SWF File Format Specification. It occurs
between the flags and buttons fields. It is initially set to 0 if there are no actions for the button. If there
are actions for the button, then it must contain the offset from the point in the SWF file following this
16-bit value to the beginning of the action offset field.

DefineButton2 =

Header
ButtonID
Flags

ActionRecordsOffset (this is missing from the spec)

Buttons
ButtonEndFlag
Button2ActionCode
ActionOffset
Condition
Action [ActionRecords]
ActionEndFlag

ActionOffset

There is one action offset per condition (mouse overDownToIdle). This is the offset used to skip over
the condition and the following actions (the ActionRecord) for the condition. You need to update
this value when adding actions.

Condition

The condition field is roughly equivalent to a wired movie event. The actions associated with button
state transition condition are triggered when the transition occurs. You need to add or edit this field.

Actions

Flash actions each have their own action tag code. QuickTime actions use a single QuickTime actions
code: 'AA'. You may add a list of actions to a single QuickTime actions tag.

The format of the QuickTime actions tag is as follows:

1 byte: // Tag = 'AA'
2 bytes: // data length (size of the QTAtomContainer)
n bytes // the data which is the QTAtomContainer holding the
// wired actions

DoAction

For DoAction, you need to modify a subset of the defineButton2 fields in the same manner as
described above. These fields are file length, the record header size portion, and the action record.

Note that you need to write the length fields in little-endian format.

224 Adding Wired Actions To a Flash Track

C H A P T E R 5

Creating Video Tracks at 30 Frames-per-Second

The duration of a video frame is stored in the time-to-sample atom contained within a sample table
atom. This duration cannot be interpreted without the media’s time scale, which defines the
units-per-second for the duration. In this example, each frame has the same duration, so the
time-to-sample atom has one entry, which applies to all video frames in the media.

As long as the ratio between frame duration and media time scale remains 1:30, any combination of
values can be used for the duration and time scale. The larger the time scale the shorter the maximum
duration. Since a movie defaults to a time scale of 600, this is a good number to use. It is also the least
common multiple for 24, 25, and 30, making it handy for much of the math you are likely to encounter
when making a movie.

The movie time scale is independent of the media time scale. Since you want to avoid movie edits
that don’t land on frame boundaries, it is a good idea to keep the movie time scale and the media
time scale the same, or the movie time scale should be an even multiple of the media time scale. The
movie time scale is stored in the movie header atom.

With a time scale of 600 in the media header atom, the time-to-sample atom would contain the
following data values:

Atom size 24

Atom type 'stts'

Version/Flags 0

Number of entries 1

Sample count n

Sample duration 20

Creating Video Tracks at 29.97 Frames-per-Second

NTSC color video is not 30 frames-per-second (fps), but actually 29.97 fps. The previous example
showed how the media time scale and the duration of the frames specify the video’s frame rate. By
setting the media’s time scale to 2997 units per second and setting the frame durations to 100 units
each, the effective rate is 29.97 fps exactly.

In this situation, it is also a good idea to set the movie time scale to 2997 in order to avoid movie edits
that don’t land on frame boundaries. The movie’s time scale is stored in the movie header atom.


Atom size 24

Atom type 'stts'

Creating Video Tracks at 30 Frames-per-Second 225

C H A P T E R 5

Version/Flags 0

Number of entries 1

Sample count n

Sample duration 100

Creating Audio Tracks at 44.1 Khz

The duration of an audio sample is stored in the time-to-sample atom contained in a sample table
atom. This duration cannot be interpreted without the media’s time scale, which defines the
units-per-second for the duration. With audio, the duration of each audio sample is typically 1, so
the time-to-sample atom has one entry, which applies to all audio samples.


Atom size 24

Atom type 'stts'

Version/Flags 0

Number of entries 1

Sample count n

Sample duration 1

This atom does not indicate whether the audio is stereo or mono or whether it contains 8-bit or 16-bit
samples. That information is stored in the sound sample description atom, which is contained in the
sample table atom.

Creating a Timecode Track for 29.97 FPS Video

A timecode track specifies timecode information for other tracks. The timecode keeps track of the
timecodes of the original source of the video and audio. After a movie has been edited, the timecode
can be extracted to determine the source tape and the timecodes of the frames.

It is important that the timecode track has the same time scale as the video track. Otherwise, the
timecode will not tick at the exact same time as the video track.

For each contiguous source tape segment, there is a single timecode sample that specifies the timecode
value corresponding to the start of the segment. From this sample, the timecode value can be
determined for any point in the segment.

226 Creating Audio Tracks at 44.1 Khz

C H A P T E R 5

The sample description for a timecode track specifies the timecode system being used (for example,
30 fps drop frame) and the source information. Each sample is a timecode value.

Since the timecode media handler is a derived from the base media handler, the media information
atom starts with a generic media header atom. The timecode atoms would contain the following data
values:

Atom size 77

Atom type 'gmhd'

Atom size 69

Atom type 'gmin'

Version/Flags 0

Graphics mode 0x0040

Opcolor (red) 0x8000

Opcolor (green) 0x8000

Opcolor (blue) 0x8000

Balance 0

Reserved 0

Atom size 45

Atom type 'tmcd'

Atom size 37

Atom type 'tcmi'

Version/Flags 0

Text font 0 (system font)

Text face 0 (plain)

Text size 12

Text color (red) 0

Text color (green) 0

Text color (blue) 0

Background color (red) 0

Background color (green) 0

Background color (blue) 0


C H A P T E R 5

Font name 'pChicago' (Pascal
string)

The sample table atom contains all the standard sample atoms and has the following data values:

Atom size 174

Atom type 'stbl' (sample table)

Atom size 74

Atom type 'stsd' (sample
description)

Version/Flags 0

Number of entries 1

Sample description size 58
[1]

Data format [1] 'tmcd'

Reserved [1] 0

Data reference index [1] 1

Flags[1] 0

Flags (timecode) [1] 7 (drop frame + 24 hour
+ negative times OK)

Time scale[1] 2997

Frame duration[1] 100

Number of frames [1] 20

Atom size 24

Atom type 'name'

String length 12

Language code 0 (English)

Name “my tape
name”

Atom size 24

Atom type 'stts' (time to sample)

Version/Flags 0

228 Creating a Timecode Track for 29.97 FPS Video

C H A P T E R 5

Number of entries 1

Sample count[1] 1

Sample duration[1] 1

Atom size 28

Atom type 'stsc' (sample to
chunk)

Version/Flags 0

Number of entries 1

First chunk[1] 1

Samples per chunk[1] 1

Sample description ID[1] 1

Atom size 20

Atom type 'stsz' (sample size)

Version/Flags 0

Sample size 4

Number of entries 1

Atom size 20

Atom type 'stco' (chunk offset)

Version/Flags 0

Number of entries 1

Offset [1] (offset into file of chunk
1)

In the example, let’s assume that the segment’s beginning timecode is 1:15:32.4 (1 hour, 15 minutes,
32 seconds, and 4 frames). The time would be expressed in the data file as 0x010F2004 (0x01 = 1 hour;
0x0F = 15 minutes; 0x20 = 32 seconds; 0x04 = 4 frames).

The video and audio tracks must contain a track reference atom to indicate that they reference this
timecode track. The track reference is the same for both and is contained in the track atom (at the
same level as the track header and media atoms).

This track reference would contain the following data values:

Atom size 12


C H A P T E R 5

Atom type 'tref'

Reference type 'tmcd'

Track ID of referenced track 3
(timecode track)

In this example, the video and sound tracks are tracks 1 and 2. The timecode track is track 3.

Playing With Edit Lists

A segment of a movie can be repeated without duplicating media data by using edit lists. Suppose
you have a single-track movie whose media time scale is 100 and track duration is 1000 (10 seconds).
For this example the movie’s time scale is 600. If there are no edits in the movie, the edit atom would
contain the following data values:

Atom size 36

Atom type 'edts'

Atom size 28

Atom type 'elst'

Version/Flags 0

Number of entries 2

Track duration 6000 (10 seconds)

Media time 0

Media rate 1.0

Because this is a single-track move, the track’s duration in the track header atom is 6000 and the
movie’s duration in the movie header atom is 6000.

If you change the track to play the media from time 0 to time 2 seconds, and then play the media from
time 0 to time 10 seconds, the edit atom would now contain these data values:

Atom size 48

Atom type 'edts'

Atom size 40

Atom type 'elst'

Version/Flags 0

230 Playing With Edit Lists

C H A P T E R 5

Number of entries 2

Track duration[1] 1200 (2 seconds)

Media time[1] 0

Media rate[1] 1.0


Media time[2] 0

Media rate[2] 1.0

Because the track is now 2 seconds longer, the track’s duration in the track header atom must now
be 7200, and the movie’s duration in the movie header atom must also be 7200.

Currently, the media plays from time 0 to time 2, then plays from time 0 to time 10. If you take that
repeated segment at the beginning (time 0 to time 2) and play it at double speed to maintain the
original duration, the edit atom would now contain the following values:

Atom size 60

Atom type 'edts'

Atom size 52

Atom type 'elst'

Version/Flags 0

Number of entries 3

Track duration[1] 600 (1 second)

Media time[1] 0

Media rate[1] 2.0

Track duration[2] 600 (1 second)

Media time[2] 0

Media rate[2] 2.0


Media time[3] 200

Media rate[3] 1.0

Because the track is now back to its original duration of 10 seconds, its duration in the track header
atom is 6000, and the movie’s duration in the movie header atom is 6000.

Playing With Edit Lists 231

C H A P T E R 5

Interleaving Movie Data

In order to get optimal movie playback, you must create the movie with interleaved data. The data
for the movie is placed on disk in time order so the data for a particular time in the movie is close
together in the file. This means that you will have to intersperse the data from different tracks. To
illustrate this, consider a movie with a single video and a single audio track.

Figure 5-7 (page 232) shows how the movie data was collected, and how the data would need to be
played back for proper synchronization. In this example, the video data is recorded at 10 frames per
second and the audio data is grouped into half-second chunks.

Figure 5-7 Non-interleaved movie data

1 sec 2 sec 3 sec
Time

Video track

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

Audio track

1 2 3 4 5 6 7

After the data has been interleaved on the disk, the movie data atom would contain movie data in
the order shown in Figure 5-8 (page 232).

Figure 5-8 Interleaved movie data

File

'moov' 'mdat'

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
1 2 3 4

In this example, the file begins with the movie atom ('moov'), followed by the movie data atom
('mdat'). In order to overcome any latencies in sound playback, at least one second of sound data is
placed at the beginning of the interleaved data. This means that the sound and video data are offset
from each other in the file by one second.

232 Interleaving Movie Data

C H A P T E R 5

Referencing Two Data Files With a Single Track

The data reference index to be used for a given media sample is stored within that sample’s sample
description. Therefore, a track must contain multiple sample descriptions in order for that track to
reference multiple data files. A different sample description must be used whenever the data file
changes or whenever the format of the data changes. The sample-to-chunk atom determines which
sample description to use for a sample.

The sample description atom would contain the following data values:

Atom size …

Atom type 'stsd'

Version/Flags 0

Number of entries 2

Sample description size[1] …

Data format 'tmcd'

Reserved 0


(sample data) …

Sample description size[1] …

Data format 'tmcd'

Reserved 0


(sample data) …

If there is only 1 sample per chunk and the first 10 samples are extracted from sample description 2
and the next 30 samples are extracted from sample description 1, the sample-to-chunk atom would
contain the following data values:

Atom size 40

Atom type 'stsc'

Version/Flags 0

Number of entries 2

First chunk[1] 1

Referencing Two Data Files With a Single Track 233

C H A P T E R 5



First chunk[2] 11



The data reference atom would contain the following data values:

Atom size …

Atom type 'dinf'

Atom size …

Atom type 'dref'

Version/Flags 0

Number of entries 2

Size[1] …

Type[1] 'alis'

Version[1] 0

Flags[1] 0 (not self referenced)

Data reference[1] [alias pointing to file #1]

Size[2] …

Type[2] 'rsrc'

Version[2] 0

Flags[2] 0 (not self referenced)

Data reference[2] [alias pointing to file #2]

Getting the Name of a QuickTime VR Node

You can use standard QuickTime atom container functions to retrieve the information in a QuickTime
VR node header atom. For example, the MyGetNodeName function defined in Listing 5-14 (page 235)
returns the name of a node, given its node ID.

234 Getting the Name of a QuickTime VR Node

C H A P T E R 5

Listing 5-14 Getting a node’s name

OSErr MyGetNodeName (QTVRInstance theInstance, UInt32 theNodeID,
StringPtr
theStringPtr)
{
OSErr theErr = noErr;
QTAtomContainer theNodeInfo;
QTVRNodeHeaderAtomPtr theNodeHeader;
QTAtom theNodeHeaderAtom = 0;

//Get the node information atom container.
theErr = QTVRGetNodeInfo(theInstance, theNodeID, &theNodeInfo);

//Get the node header atom.
if (!theErr)
theNodeHeaderAtom = QTFindChildByID(theNodeInfo, kParentAtomIsContainer,

kQTVRNodeHeaderAtomType, 1,
nil);
if (theNodeHeaderAtom != 0) {
QTLockContainer(theNodeInfo);

//Get a pointer to the node header atom data.
theErr = QTGetAtomDataPtr(theNodeInfo, theNodeHeaderAtom, nil,
(Ptr
*)&theNodeHeader);
//See if there is a name atom.
if (!theErr && theNodeHeader->nameAtomID != 0) {
QTAtom theNameAtom;
theNameAtom = QTFindChildByID(theNodeInfo, kParentAtomIsContainer,

kQTVRStringAtomType, theNodeHeader->nameAtomID,
nil);
if (theNameAtom != 0) {
VRStringAtomPtr theStringAtomPtr;

//Get a pointer to the name atom data; copy it into the string.
theErr = QTGetAtomDataPtr(theNodeInfo, theNameAtom, nil,
(Ptr
*)&theStringAtomPtr);
if (!theErr) {
short theLen = theStringAtomPtr->stringLength;
if (theLen > 255)
theLen = 255;
BlockMove(theStringAtomPtr->string, &theStringPtr[1], theLen);
theStringPtr[0] = theLen;
}
}
}
QTUnlockContainer(theNodeInfo);
}

QTDisposeAtomContainer(theNodeInfo);
return(theErr);
}

Getting the Name of a QuickTime VR Node 235

C H A P T E R 5

The MyGetNodeName function defined in Listing 5-14 (page 235) retrieves the node information atom
container (by calling QTVRGetNodeInfo) and then looks inside that container for the node header
atom with atom ID 1. If it finds one, it locks the container and then gets a pointer to the node header
atom data. The desired information, the node name, is contained in the string atom whose atom ID
is specified by the nameAtomID field of the node header structure. Accordingly, the MyGetNodeName
function then calls QTFindChildByID once again to find that string atom. If the string atom is found,
MyGetNodeName calls QTGetAtomDataPtr to get a pointer to the string atom data. Finally,
MyGetNodeName copies the string data into the appropriate location and cleans up after itself before
returning.

Adding Custom Atoms in a QuickTime VR Movie

If you author a QuickTime VR movie, you may choose to add custom atoms to either the VR world
or node information atom containers. Those atoms can be extracted within an application to provide
additional information that the application may use.

Information that pertains to the entire scene might be stored in a custom atom within the VR world
atom container. Node-specific information could be stored in the individual node information atom
containers or as sibling atoms to the node location atoms within the VR world.

Custom hot spot atoms should be stored as siblings to the hot spot information atoms in the node
information atom container. Generally, its atom type is the same as the custom hot spot type. You
can set up an intercept procedure in your application in order to process clicks on the custom hot
spots.

If you use custom atoms, you should install your hot spot intercept procedure when you open the
movie. Listing 5-15 (page 236) is an example of such an intercept procedure.

Listing 5-15 Typical hot spot intercept procedure

QTVRInterceptProc MyProc = NewQTVRInterceptProc (MyHotSpot);
QTVRInstallInterceptProc (qtvr, kQTVRTriggerHotSpotSelector, myProc, 0, 0);

pascal void MyHotSpot (QTVRInstance qtvr, QTVRInterceptPtr qtvrMsg,
SInt32 refCon, Boolean *cancel)
{
UInt32 hotSpotID = (UInt32) qtvrMsg->parameter[0];
QTAtomContainer nodeInfo =
(QTAtomContainer) qtvrMsg->parameter[1];
QTAtom hotSpotAtom = (QTAtom) qtvrMsg->parameter[2];
OSType hotSpotType;
CustomData myCustomData;
QTAtom myAtom;

QTVRGetHotSpotType (qtvr, hotSpotID, &hotSpotType);
if (hotSpotType != kMyAtomType) return;

// It's our type of hot spot - don't let anyone else handle it
*cancel = true;

// Find our custom atom
myAtom = QTFindChildByID (nodeInfo, hotSpotAtom, kMyAtomType, 1, nil);
if (myAtom != 0) {

236 Adding Custom Atoms in a QuickTime VR Movie

C H A P T E R 5

OSErr err;
// Copy the custom data into our structure
err = QTCopyAtomDataToPtr (nodeInfo, myAtom, false,
sizeof(CustomData), &myCustomData, nil);
if (err == noErr)
// Do something with it
DoMyHotSpotStuff (hotSpotID, &myCustomData);
}
}

Your intercept procedure is called for clicks on any hot spot. You should check to see if it is your type
of hot spot and if so, extract the custom hot spot atom and do whatever is appropriate for your hot
spot type (DoMyHotSpotStuff).

When you no longer need the intercept procedure you should call QTVRInstallInterceptProc again
with the same selector and a nil procedure pointer and then call DisposeRoutineDescriptor on
myProc.

Apple reserves all hot spot and atom types with lowercase letters. Your custom hot spot type should
contain all uppercase letters.

Adding Atom Containers in a QuickTime VR Movie

Assuming you have already created the QuickTime VR world and node information atom containers,
Listing 5-16 (page 237) shows the code (minus error checking) you would use to add them to the QTVR
track.

Listing 5-16 Adding atom containers to a track

long descSize;
QTVRSampleDescriptionHandle qtvrSampleDesc;

// Create a QTVR sample description handle

descSize = sizeof(QTVRSampleDescription) + GetHandleSize((Handle) vrWorld) -
sizeof(UInt32);
qtvrSampleDesc = (QTVRSampleDescriptionHandle) NewHandleClear (descSize);
(*qtvrSampleDesc)->size = descSize;
(*qtvrSampleDesc)->type = kQTVRQTVRType;

// Copy the VR world atom container data into the QTVR sample description
BlockMove (*((Handle) vrWorld), &((*qtvrSampleDesc)->data),
GetHandleSize((Handle) vrWorld));
// Now add it to the QTVR track's media
err = BeginMediaEdits (qtvrMedia);
err = AddMediaSample (qtvrMedia, (Handle) nodeInfo, 0,
GetHandleSize((Handle) nodeInfo), duration,
(SampleDescriptionHandle) qtvrSampleDesc, 1, 0, &sampleTime);
err = EndMediaEdits (qtvrMedia);
InsertMediaIntoTrack (qtvrTrack, trackTime, sampleTime, duration, 1L<<16);

Adding Atom Containers in a QuickTime VR Movie 237

C H A P T E R 5

The duration value is computed based on the duration of the corresponding image track samples
for the node. The value of trackTime is the time for the beginning of the current node (zero for a
single node movie). The values of duration and sampleTime are in the time base of the media; the
value of trackTime is in the movie’s time base.

Optimizing QuickTime VR Movies for Web Playback

Originally, both QuickTime movies and QuickTime VR movies had to be completely downloaded to
the user’s local hard disk before they could be viewed. Starting with QuickTime 2.5, if the movie data
is properly laid out in the file, standard linear QuickTime movies can be viewed almost immediately.
The frames that have been downloaded so far are shown while subsequent frames continue to be
downloaded.

The important change that took place to allow this to happen was for QuickTime to place global movie
information at the beginning of the file. Originally, it was at the end of the file. After that, the frame
data simply needs to be in order in the file. Similarly, QuickTime VR files also need to be laid out in
a certain manner in order to get some sort of quick feedback when viewing on the Web. Roughly
speaking this involves writing out all of the media samples in the file in a particular order. Apple
now provides a movie export component that does this for you: the QTVR Flattener.

The QTVR Flattener
The QTVR Flattener is a movie export component that converts an existing QuickTime VR single
node movie into a new movie that is optimized for the Web. Not only does the flattener reorder the
media samples, but for panoramas it also creates a small preview of the panorama. When viewed on
the Web, this preview appears after 5% to 10% of the movie data has been downloaded, allowing
users to see a lower-resolution version of the panorama.

Using the QTVR Flattener from your application is quite easy. After you have created the QuickTime
VR movie, you simply open the QTVR Flattener component and call the MovieExportToFile routine
as shown in Listing 5-17 (page 238).

Listing 5-17 Using the flattener

ComponentDescription desc;
Component flattener;
ComponentInstance qtvrExport = nil;
desc.componentType = MovieExportType;
desc.componentSubType = MovieFileType;
desc.componentManufacturer = QTVRFlattenerType;
flattener = FindNextComponent(nil, &desc);
if (flattener) qtvrExport = OpenComponent (flattener);
if (qtvrExport)
MovieExportToFile (qtvrExport, &myFileSpec, myQTVRMovie, nil, 0, 0);

The code fragment shown in Listing 5-17 (page 238) creates a flattened movie file specified by the
myFileSpec parameter. If your QuickTime VR movie is a panorama, the flattened movie file includes
a quarter size, blurred JPEG, compressed preview of the panorama image.

238 Optimizing QuickTime VR Movies for Web Playback

C H A P T E R 5

Note: The constants MovieExportType and MovieFileType used in Listing 5-17 (page 238) are defined
in header files QuickTimeComponents.h and Movies.h respectively and are defined as 'spit' and
'MooV'. <8bat>u

You can present users with the QTVR Flattener’s own dialog box to allow them to choose options
such as how to compress the preview image or to select a separate preview image file. Use the following
code to show the dialog box:

err = MovieExportDoUserDialog (qtvrExport, myQTVRMovie, nil, 0, 0,
&cancel);

If the user cancels the dialog box, then the Boolean cancel is set to true.

If you do not want to present the user with the flattener’s dialog box, you can communicate directly
with the component by using the MovieExportSetSettingsFromAtomContainer routine as described
in the following paragraphs.

If you want to specify a preview image other than the default, you need to create a special atom
container and then call MovieExportSetSettingsFromAtomContainer before calling
MovieExportToFile. You can specify how to compress the image, what resolution to use, and you
can even specify your own preview image file to be used. The atom container you pass in can have
various atoms that specify certain export options. These atoms must all be children of a flattener
settings parent atom.

The preview resolution atom is a 16-bit value that allows you to specify the resolution of the preview
image. This value, which defaults to kQTVRQuarterRes, indicates how much to reduce the preview
image.

The blur preview atom is a Boolean value that indicates whether to blur the image before compressing.
Blurring usually results in a much more highly compressed image. The default value is true.

The create preview atom is a Boolean value that indicates whether a preview image should be created.
The default value is true.

The import preview atom is a Boolean value that is used to indicate that the preview image should
be imported from an external file rather than generated from the image in the panorama file itself.
This allows you to have any image you want as the preview for the panorama. You can specify which
file to use by also including the import specification atom, which is an FSSpec data structure that
identifies the image file. If you do not include this atom, then the flattener presents the user with a
dialog box asking the user to select a file. The default for import preview is false. If an import file
is used, the image is used at its natural size and the resolution setting is ignored.

Sample Atom Container for the QTVR Flattener
The sample code in Listing 5-18 (page 239) creates an atom container and adds atoms to indicate an
import preview file for the flattener to use.

Listing 5-18 Specifying a preview file for the flattener to use

Boolean yes = true;
QTAtomContainer exportData;
QTAtom parent;

Optimizing QuickTime VR Movies for Web Playback 239

C H A P T E R 5

err = QTNewAtomContainer(&exportData);
// create a parent for the other settings atoms
err = QTInsertChild (exportData, kParentAtomIsContainer,
QTVRFlattenerParentAtomType, 1, 0, 0, nil, &parent);
// Add child atom to indicate we want to import the preview from a file
err = QTInsertChild (exportData, parent, QTVRImportPreviewAtomType, 1, 0,
sizeof (yes), &yes, nil);
// Add child atom to tell which file to import
err = QTInsertChild (exportData, parent, QTVRImportSpecAtomType, 1, 0,
sizeof (previewSpec), &previewSpec, nil);
// Tell the export component
MovieExportSetSettingsFromAtomContainer (qtvrExport, exportData);

Overriding the compression settings is a bit more complicated. You need to open a standard image
compression dialog component and make calls to obtain an atom container that you can then pass to
the QTVR Flattener component.

Listing 5-19 Overriding the compression settings

ComponentInstance sc;
QTAtomContainer compressorData;
SCSpatialSettings ss;
sc = OpenDefaultComponent(StandardCompressionType,StandardCompressionSubType);
ss.codecType = kCinepakCodecType;
ss.codec = nil;
ss.depth = 0;
ss.spatialQuality = codecHighQuality
err = SCSetInfo(sc, scSpatialSettingsType, &ss);
err = SCGetSettingsAsAtomContainer(sc, &compressorData);
MovieExportSetSettingsFromAtomContainer (qtvrExport, compressorData);

240 Optimizing QuickTime VR Movies for Web Playback

A P P E N D I X A

QuickTime Image File Format

This appendix describes QuickTime image files, which are intended to provide the most useful
container for QuickTime-compressed still images.

Most still image file formats define both how images should be stored and compressed. However,
the QuickTime image file format is a container format, which describes a storage mechanism
independent of compression. The QuickTime image file format uses the same atom-based structure
as a QuickTime movie.

Atom Types in QuickTime Image Files

There are two mandatory atom types: 'idsc', which contains an image description, and 'idat',
which contains the image data. This is illustrated in Figure A-1 (page 242). A QuickTime image file
can also contain other atoms. For example, it can contain single-fork preview atoms.

In QuickTime 4, there is a new optional atom type: 'iicc', which can store a ColorSync profile.

Figure A-1 (page 242) shows an example QuickTime image file containing a JPEG-compressed image.

Atom Types in QuickTime Image Files 241

A P P E N D I X A

Figure A-1 An 'idsc' atom followed by an 'idat' atom

Bytes
Image description atom

Atom size 4

Type = 'idsc' 4

Image description Variable

Image data atom

Atom size 4

Type = 'idat' 4

Image data Variable

Table A-1 A QuickTime image file containing JPEG-compressed data

0000005E Atom size, 94 bytes

69647363 Atom type, 'idsc'

00000056 Image description size, 86 bytes

6A706567 Compressor identifier, 'jpeg'

00000000 Reserved, set to 0



00000000 Major and minor version of this data, 0 if not
applicable

6170706C Vendor who compressed this data, 'appl'

00000000 Temporal quality, 0 (no temporal compression)

00000200 Spatial quality, codecNormalQuality

0140 Image width, 320

00F0 Image height, 240

00480000 Horizontal resolution, 72 dpi

00480000 Vertical resolution, 72 dpi

00003C57 Data size, 15447 bytes (use 0 if unknown)

242 Atom Types in QuickTime Image Files

A P P E N D I X A

0001 Frame count, 1

0C 50 68 6F 74 6F 20 2D20 Compressor name, "Photo - JPEG" (32-byte Pascal
4A 50 45 47 00 00 00 string)
00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00

0018 Image bit depth, 24

FFFF Color lookup table ID, -1 (none)

00003C5F Atom size, 15455 bytes

69646174 Atom type, 'idat'

FF D8 FF E0 00 10 4A 46 JPEG compressed data
49 46 00 01 01 01 00 48
...

Important: The exact order and size of atoms is not guaranteed to match the example in Figure
A-1 (page 242). Applications reading QuickTime image files should always use the atom size to traverse
the file and ignore atoms of unrecognized types. s

Note: Like QuickTime movie files, QuickTime image files are big-endian. However, image data is
stored in the same byte order as usually specified by the particular compression format. u

Recommended File Type and Suffix

Because the QuickTime image file is a single-fork format, it works well in cross-platform applications.
On Mac OS systems, QuickTime image files are identified by the file type 'qtif'. Apple recommends
using the filename extension .QIF to identify QuickTime image files on other platforms.

Recommended File Type and Suffix 243

A P P E N D I X A

244 Recommended File Type and Suffix

A P P E N D I X B

Defining Media Data Layouts

The QuickTime file format provides a great deal of flexibility in how media data is physically arranged
within a file. However, it also allows media layouts to be created that may be inefficient for playback
on a given device. To complicate the matter, a media layout that is inefficient for one device may be,
in fact, very efficient for another. The purpose of this appendix is to define some common uses of
QuickTime files and describe the media layout in these circumstances.

A QuickTime file can reference media data stored in a number of files, including the file itself. If a
QuickTime file references only media data contained within itself, the file is said to be self-contained.
A QuickTime file can also reference media data stored in files that are not QuickTime files. This is
because the QuickTime file format references media within a URL by file offset, rather than by a data
structuring mechanism of a particular file format. This allows a QuickTime file to refer to data stored
in any container format.

Often, it is convenient to store a single media stream per file, for example, when encoding content. It
is also useful for purposes of reusing content. (To reuse an elementary stream, it is not necessary to
extract it from a larger, possibly multiplexed file.)

Because QuickTime can reference media stored in any file, it is not required that media be stored in
the QuickTime file format. However, this is recommended. Putting the elementary streams in a
QuickTime file has several advantages, particularly in enabling interchange of the content between
different tools. Further, the QuickTime file format adds very little overhead to the media—as little as
a few hundred bytes in many cases—so there is no great penalty in storage space.

One of the issues facing any device (a server or a local workstation) that is attempting to play back a
QuickTime file in real time is the number of file seeks that must be performed.

It is possible to arrange the data in a QuickTime file to minimize, and potentially eliminate, any seeks
during the course of normal playback. (Of course, random access and other kinds of interactivity
require seeks.) Minimizing seeks is accomplished by interleaving the media data in the QuickTime
file in such a way that the layout of the media in the file corresponds to the order in which the media
data will be required. It is expected that most servers, for example, will stream QuickTime media
using the facilities of the hint tracks.

Take a scenario where the QuickTime file contains a single hint track that references an audio and a
visual media stream. In order to eliminate all seeks, the hint track media must be interleaved with
the audio and visual stream data. Because the hint track sample must always be read before the audio
and visual media that it references, the hint track samples must always immediately precede the
samples they reference.

A simple illustration of the ordering of data (that is, time and file offset increasing from left to right)
is as follows:

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Defining Media Data Layouts

H0 A0 H1 V1 H2 V2 H3 A1 H4 A2 V3 H5 V4

When a single hint sample references multiple pieces of media data, those pieces of media data must
occur in the order that they are referenced.

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A P P E N D I X C

Random Access

This appendix describes how to seek with a QuickTime file using child atoms.

Seeking with a QuickTime file is accomplished primarily by using the child atoms contained in the
sample table atom. If an edit list is present, it must also be consulted. If you want to seek a given track
to a time T, where T is in the time scale of the movie header atom, you could perform the following
operations:

1. If the track contains an edit list, determine which edit contains the time T by iterating over the
edits. The start time of the edit in the movie time scale must then be subtracted from the time T
to generate T', the duration into the edit in the movie time scale. T' is next converted to the time
scale of the track’s media to generate T''. Finally, the time in the media scale to use is calculated
by adding the media start time of the edit to T''.

2. The time-to-sample atom for a track indicates what times are associated with which sample for
that track. Use this atom to find the first sample prior to the given time.

3. The sample that was located in step 1 may not be a random access point. Locating the nearest
random access point requires consulting two atoms. The sync sample table indicates which
samples are in fact random access points. Using this table, you can locate which is the first sync
sample prior to the specified time. The absence of the sync sample table indicates that all samples
are synchronization points, and makes this problem easy. The shadow sync atom gives the
opportunity for a content author to provide samples that are not delivered in the normal course
of delivery, but which can be inserted to provide additional random access points. This improves
random access without impacting bitrate during normal delivery. This atom maps samples that
are not random access points to alternate samples which are. You should also consult this table
if present to find the first shadow sync sample prior to the sample in question. Having consulted
the sync sample table and the shadow sync table, you probably wish to seek to whichever resultant
sample is closest to, but prior to, the sample found in step 1.

4. At this point you know the sample that will be used for random access. Use the sample-to-chunk
table to determine in which chunk this sample is located.

5. Knowing which chunk contained the sample in question, use the chunk offset atom to figure out
where that chunk begins.

6. Starting from this offset, you can use the information contained in the sample-to-chunk atom and
the sample size atom to figure out where within this chunk the sample in question is located. This
is the desired information.

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Random Access

248

A P P E N D I X D

Meta-Data Handling

This appendix describes how meta-data is handled when QuickTime imports other file formats. (For
more information about meta-data, refer to “Introduction to Atoms” (page 17) and “Compressed
Movie Resources” (page 83)).

These formats are grouped into the following categories and sections:

■ “Digital Video File Formats” (page 249)
■ “Digital Audio File Formats” (page 250)
■ “Still Image File Formats” (page 251)
■ “Animation and 3D File Formats” (page 253)

Each section includes a table with specific details on the following, where applicable:

■ the format supported by QuickTime––for example, the movie import component or the graphics
import component
■ the Macintosh file type––for example, 'Mp3 '
■ file name extensions––for example, .mp3
■ specific details for meta-data handling––for example, all Microsoft-defined “tombstone” data is
transferred to the imported movie’s user data. Meta-data fields that have QuickTime equivalents
are mapped as follows.
■ software required––for example, QuickTime 3 or later

Digital Video File Formats

OpenDML and other AVI
Description
files

Supported by Movie import component

Macintosh file type 'VfW '

File name extensions .avi

Digital Video File Formats 249

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Meta-Data Handling

OpenDML and other AVI
Description
files

Meta-data handling All Microsoft-defined “tombstone” data is transferred
to the imported movie’s user data. Meta-data fields that
have QuickTime equivalents are mapped as follows:
'ICOP' maps to kUserDataTextCopyright, 'ISBJ' maps
to kUserDataTextInformation, 'INAM' maps to
kUserDataTextFullName, 'ICRD' maps to '©day',
'IMED' maps to '©fmt', 'ISRC' maps to '©src'.Where
no QuickTime equivalent exists, the metadata item’s
four-character code is modified by replacing the initial
I with a ©. All other characters remain unchanged.

Software required QuickTime 3

Digital Audio File Formats

MPEG 1 layer 3 Description


Macintosh file type 'Mp3 ', 'SwaT', 'MPEG', 'PLAY', 'MPG3', 'MP3 '

File name extensions .mp3, .swa

Meta-data handling Metadata from ID3v1-style MP3 files is imported into
the QuickTime movie.Title maps to
kUserDataTextFullName, artist maps to '©ART', album
maps to '©alb', year maps to '©day', comment maps
to '©cmt', and track number maps to '©des'.


WAV Description


Macintosh file type 'WAVE', '.WAV'

File name extensions .wav

250 Digital Audio File Formats

A P P E N D I X D
Meta-Data Handling

WAV Description

Meta-data handling All Microsoft-defined “tombstone” data is transferred
to the imported movie’s user data. Meta-data fields that
have QuickTime equivalents are mapped as follows:
'ICOP' maps to kUserDataTextCopyright, 'ISBJ' maps
to kUserDataTextInformation, 'INAM' maps to
kUserDataTextFullName, 'ICRD' maps to '©day',
'IMED' maps to '©fmt', 'ISRC' maps to '©src'.Where
no QuickTime equivalent exists, the metadata item’s
four-character code is modified by replacing the initial
I with a ©. All other characters remain unchanged.

Software required QuickTime 2.5 or later

Still Image File Formats

FlashPix Description

Supported by Graphics import component

Macintosh file type 'FPix'

File name extensions .fpx

Meta-data handling Information about copyright, authorship, caption text,
content description notes, camera manufacturer name,
camera model name are transferred to
kUserDataTextCopyright,
kUserDataTextArtistField, kUserDataTextFullName,
kParameterInfoWindowTitle,
kParameterInfoManufacturer,
kUserDataTextMakeField user data items, respectively.

Formats supported 1.0


GIF Description


Macintosh file type 'GIFf', or 'GIF '

File name extensions .gif

Meta-data handling The GIF comment field is transferred to the
kUserDataDateTextInformation user data item.


Still Image File Formats 251

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Meta-Data Handling

JFIF/JPEG Description


Macintosh file type 'JPEG’

File name extensions .jpg

Meta-data handling The JFIF comment field is transferred to the imported
Movie’s user data in the kUserDataTextInformation
field.


Photoshop Description


Macintosh file type '8BPS'

File name extensions .psd

Meta-data handling Photoshop files store their metadata based on the
IPTC-NAA Information Interchange Model and Digital
Newsphoto Parameter Record. This information is
transferred into the importer Movie’s user data. The
entire ITPC-NAA record is placed into a user data item
of type 'iptc'. In addition, those metadata items which
are defined by QuickTime are mapped directly to
QuickTime types as follows: 116 to
kUserDataTextCopyright, 120 to
kUserDataTextInformation, 105 to
kUserDataTextFullName, 55 to '©day', 115 to '©src'.

Software required QuickTime 2.5 or later. QuickTime 3 is required for
metadata handling.

QuickTime Image File Description


Macintosh file type 'qtif'

File name extensions .qtif, .qif, .qti

Meta-data handling Metadata that is stored in
quickTimeImageFileMetaDataAtom atom is copied
directly to the Movie’s user data.

Formats supported All


252 Still Image File Formats

A P P E N D I X D
Meta-Data Handling

TIFF Description

Supported by Graphics Import Component

Macintosh file type 'TIFF'

File name extensions .tif, .tiff

Meta-data handling Extracted from standard tags and from IPTC block

Software required QuickTime 3 or later

Animation and 3D File Formats

Animated GIF Description


Macintosh file type 'GIFf'

File name extensions .gif

Meta-data handling The GIF comment field is transferred to
kUserDataTextInformation user data item.

Software required QuickTime 3 or later

Animation and 3D File Formats 253

A P P E N D I X D
Meta-Data Handling

254 Animation and 3D File Formats

A P P E N D I X E

Summary of VR World and Node Atom
Types

This appendix includes information that pertains to Chapter 3, “VR World Atom Container” (page 164)
and “Node Information Atom Container” (page 169).

C Summary

Constants

VR World Atom Types

enum {
kQTVRWorldHeaderAtomType = FOUR_CHAR_CODE('vrsc'),
kQTVRImagingParentAtomType = FOUR_CHAR_CODE('imgp'),
kQTVRPanoImagingAtomType = FOUR_CHAR_CODE('impn'),
kQTVRObjectImagingAtomType = FOUR_CHAR_CODE('imob'),
kQTVRNodeParentAtomType = FOUR_CHAR_CODE('vrnp'),
kQTVRNodeIDAtomType = FOUR_CHAR_CODE('vrni'),
kQTVRNodeLocationAtomType = FOUR_CHAR_CODE('nloc')
};

Node Information Atom Types

enum {
kQTVRNodeHeaderAtomType = FOUR_CHAR_CODE('ndhd'),
kQTVRHotSpotParentAtomType = FOUR_CHAR_CODE('hspa'),
kQTVRHotSpotAtomType = FOUR_CHAR_CODE('hots'),
kQTVRHotSpotInfoAtomType = FOUR_CHAR_CODE('hsin'),
kQTVRLinkInfoAtomType = FOUR_CHAR_CODE('link')
};

Miscellaneous Atom Types

enum {
kQTVRStringAtomType = FOUR_CHAR_CODE('vrsg'),
kQTVRPanoSampleDataAtomType = FOUR_CHAR_CODE('pdat'),
kQTVRObjectInfoAtomType = FOUR_CHAR_CODE('obji'),

C Summary 255

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Summary of VR World and Node Atom Types

kQTVRAltImageTrackRefAtomType = FOUR_CHAR_CODE('imtr'),
kQTVRAltHotSpotTrackRefAtomType = FOUR_CHAR_CODE('hstr'),
kQTVRAngleRangeAtomType = FOUR_CHAR_CODE('arng'),
kQTVRTrackRefArrayAtomType = FOUR_CHAR_CODE('tref'),
kQTVRPanConstraintAtomType = FOUR_CHAR_CODE('pcon'),
kQTVRTiltConstraintAtomType = FOUR_CHAR_CODE('tcon'),
kQTVRFOVConstraintAtomType = FOUR_CHAR_CODE('fcon'),
kQTVRCubicViewAtomType = FOUR_CHAR_CODE('cuvw'),
kQTVRCubicFaceDataAtomType = FOUR_CHAR_CODE('cufa')
};

Track Reference Types

enum {
kQTVRImageTrackRefType = FOUR_CHAR_CODE('imgt'),
kQTVRHotSpotTrackRefType = FOUR_CHAR_CODE('hott')
};

Imaging Property Valid Flags

enum {
kQTVRValidCorrection = 1 << 0,
kQTVRValidQuality = 1 << 1,
kQTVRValidDirectDraw = 1 << 2,
kQTVRValidFirstExtraProperty = 1 << 3
};

Link Hot Spot Valid Bits

enum {
kQTVRValidPan = 1 << 0,
kQTVRValidTilt = 1 << 1,
kQTVRValidFOV = 1 << 2,
kQTVRValidViewCenter = 1 << 3
};

Animation Settings

enum QTVRAnimationSettings {
kQTVRObjectAnimateViewFramesOn = (1 << 0),
kQTVRObjectPalindromeViewFramesOn = (1 << 1),
kQTVRObjectStartFirstViewFrameOn = (1 << 2),
kQTVRObjectAnimateViewsOn = (1 << 3),
kQTVRObjectPalindromeViewsOn = (1 << 4),
kQTVRObjectSyncViewToFrameRate = (1 << 5),
kQTVRObjectDontLoopViewFramesOn = (1 << 6),
kQTVRObjectPlayEveryViewFrameOn = (1 << 7)
};

Control Settings

enum QTVRControlSettings {
kQTVRObjectWrapPanOn = (1 << 0),

256 C Summary

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kQTVRObjectWrapTiltOn = (1 << 1),
kQTVRObjectCanZoomOn = (1 << 2),
kQTVRObjectReverseHControlOn = (1 << 3),
kQTVRObjectReverseVControlOn = (1 << 4),
kQTVRObjectSwapHVControlOn = (1 << 5),
kQTVRObjectTranslationOn = (1 << 6)
};

Controller Subtype and ID

enum {
kQTControllerType = FOUR_CHAR_CODE('ctyp').
kQTControllerID = 1
};

Object Controller Types

enum ObjectUITypes {
kGrabberScrollerUI = 1,
kOldJoyStickUI = 2,
kJoystickUI = 3,
kGrabberUI = 4,
kAbsoluteUI = 5
};

Node Location Flag

enum {
kQTVRSameFile = 0
};

Panorama Sample Flag

enum {
kQTVRPanoFlagHorizontal = 1 << 0,
kQTVRPanoFlagAlwaysWrap = 1 << 2
};

Data Types
typedef float Float32;

Sample Description Header Structure

typedef struct QTVRSampleDescription {
UInt32 size;
UInt32 type;
UInt32 reserved1;
UInt16 reserved2;
UInt16 dataRefIndex;
UInt32 data;

C Summary 257

A P P E N D I X E

} QTVRSampleDescription, *QTVRSampleDescriptionPtr, **QTVRSampleDescriptionHandle;

String Atom Structure

typedef struct QTVRStringAtom {
UInt16 stringUsage;
UInt16 stringLength;
unsigned char string[4];
} QTVRStringAtom, *QTVRStringAtomPtr;

VR World Header Atom Structure

typedef struct QTVRWorldHeaderAtom {
UInt32 defaultNodeID;
UInt32 vrWorldFlags;
UInt32 reserved1;
UInt32 reserved2;
} QTVRWorldHeaderAtom, *QTVRWorldHeaderAtomPtr;

Panorama-Imaging Atom Structure

typedef struct QTVRPanoImagingAtom {
UInt32 imagingMode;
UInt32 imagingValidFlags;
UInt32 correction;
UInt32 quality;
UInt32 directDraw;
UInt32 imagingProperties[6];
UInt32 reserved1;
UInt32 reserved2;
} QTVRPanoImagingAtom, *QTVRPanoImagingAtomPtr;

Node Location Atom Structure

typedef struct QTVRNodeLocationAtom {
OSType nodeType;
UInt32 locationFlags;
UInt32 locationData;
UInt32 reserved1;
UInt32 reserved2;
} QTVRNodeLocationAtom, *QTVRNodeLocationAtomPtr;

Node Header Atom Structure

typedef struct QTVRNodeHeaderAtom {

258 C Summary

A P P E N D I X E

OSType nodeType;
QTAtomID nodeID;
UInt32 reserved1;
UInt32 reserved2;
} QTVRNodeHeaderAtom, *QTVRNodeHeaderAtomPtr;

Hot Spot Information Atom Structure

typedef struct QTVRHotSpotInfoAtom {
OSType hotSpotType;
SInt32 cursorID[3];
Float32 bestPan;
Float32 bestTilt;
Float32 bestFOV;
FloatPoint bestViewCenter;
Rect hotSpotRect;
UInt32 flags;
UInt32 reserved1;
UInt32 reserved2;
} QTVRHotSpotInfoAtom, *QTVRHotSpotInfoAtomPtr;

Link Hot Spot Atom Structure

typedef struct QTVRLinkHotSpotAtom {
UInt32 toNodeID;
UInt32 fromValidFlags;
Float32 fromPan;
Float32 fromTilt;
Float32 fromFOV;
FloatPoint fromViewCenter;
UInt32 toValidFlags;
Float32 toPan;
Float32 toTilt;
Float32 toFOV;
FloatPoint toViewCenter;
Float32 distance;
UInt32 flags;
UInt32 reserved1;
UInt32 reserved2;
} QTVRLinkHotSpotAtom, *QTVRLinkHotSpotAtomPtr;

Angle Range Atom Structure

typedef struct QTVRAngleRangeAtom {
Float32 minimumAngle;
Float32 maximumAngle;

C Summary 259

A P P E N D I X E

} QTVRAngleRangeAtom, *QTVRAngleRangeAtomPtr;

Panorama Sample Atom Structure

typedef struct QTVRPanoSampleAtom {
UInt32 imageRefTrackIndex;
UInt32 hotSpotRefTrackIndex;
Float32 minPan;
Float32 maxPan;
Float32 minTilt;
Float32 maxTilt;
Float32 defaultPan;
UInt32 imageSizeX;
UInt32 imageSizeY;
UInt16 imageNumFramesX;
UInt16 imageNumFramesY;
UInt32 hotSpotSizeX;
UInt32 hotSpotSizeY;
UInt16 hotSpotNumFramesX;
UInt16 hotSpotNumFramesY;
UInt32 flags;
UInt32 reserved1;
UInt32 reserved2;
} QTVRPanoSampleAtom, *QTVRPanoSampleAtomPtr;

Cubic View Atom Structure

struct QTVRCubicViewAtom {
Float32 minPan;
Float32 maxPan;
Float32 minTilt;
Float32 maxTilt;

Float32 defaultPan;
};
typedef struct QTVRCubicViewAtom QTVRCubicViewAtom;

Cubic Face Data Atom Structure

struct QTVRCubicFaceData {
float orientation[4];
float center[2];
float aspect;
float skew;
};

260 C Summary

A P P E N D I X E

typedef struct QTVRCubicFaceData QTVRCubicFaceData;

Object Sample Atom Structure

typedef struct QTVRObjectSampleAtom {
UInt16 movieType;
UInt16 viewStateCount;
UInt16 defaultViewState;
UInt16 mouseDownViewState;
UInt32 viewDuration;
UInt32 columns;
UInt32 rows;
Float32 mouseMotionScale;
Float32 minPan;
Float32 maxPan;
Float32 defaultPan;
Float32 minTilt;
Float32 maxTilt;
Float32 fieldOfView;
Float32 defaultViewCenterH;
Float32 defaultViewCenterV;
Float32 viewRate;
Float32 frameRate;
UInt32 animationSettings;
UInt32 controlSettings;
} QTVRObjectSampleAtom, *QTVRObjectSampleAtomPtr;

Track Reference Entry Structure

struct QTVRTrackRefEntry {
UInt32 trackRefType;
UInt16 trackResolution;
UInt32 trackRefIndex;
};
typedef struct QTVRTrackRefEntry QTVRTrackRefEntry;

C Summary 261

A P P E N D I X E

262 C Summary

Glossary

alpha channel The upper bits of a display pixel, chapter list A set of named entry points into a movie,
which control the blending of video and graphical presented to the viewer as a text list.
image data for a video digitizer component.
child atom A QT atom inside a container atom, which
alternate track A movie track that contains alternate is its parent atom. See also QT atom, container atom
data for another track. QuickTime chooses one track , and parent atom.
to be used when the movie is played. The choice may
be based on such considerations as image quality or chunk A collection of sample data in a media.
localization. See also track. Chunks, which may contain one or more samples,
allow optimized data access. Chunks in a media may
API (Application Programming Interface) The set have different sizes, and the samples within a chunk
of function calls, data structures, and other may have different sizes.
programming elements by which a structure of code
(such as a system-level toolbox) can be accesses by classic atom A QuickTime atom that contains no
other code (such as an application program). other atoms. A classic atom, however, may contain a
table. An example of a classic atom is an edit list atom,
atom The basic unit of data in a movie resource, containing the edit list table. Compare QT atom.
sprite, or other QuickTime data structure. There are
a number of different atom types, including movie clipped movie boundary region The region that
atoms, track atoms, and media atoms. There are two combines the union of all track movie boundary
varieties of atoms: QT atoms, which may contain other regions for a movie, which is the movie’s movie
atoms, and classic atoms, which do not contain any boundary region, with the movie’s movie clipping
other atoms. See also movie resource, sprite , QT region, which defines the portion of the movie
atom , and classic atom. boundary region that is to be used. See also movie
boundary region and movie clipping region.
atom container A tree-structured hierarchy of QT
atoms. See also QT atom. clipping The process of defining the boundaries of
a graphics area.
atom ID A 32-bit integer that uniquely identifies an
atom among other child atoms of the same parent container atom An atom that contains other atoms,
atom. The root atom has an atom ID value of 0x0001. possibly including other container atoms.
See also child atom, parent atom , and root atom. creator signature In the Macintosh file system, a
atom type A 32-bit value that uniquely identifies the four-character code that identifies the application
data type of an atom. It is normally an OSType, program to which a file belongs.
rendered by four ASCII characters. An atom’s data data fork In a Macintosh file, the section that
type helps determine how the atom’s contents are corresponds to a DOS/Windows file.
interpreted.
data handler A piece of software that is responsible
background color The color of the background for reading and writing a media’s data. The data
behind a sprite or other image. handler provides data input and output services to
bit depth The number of bits used to encode the the media’s media handler. See also media handler.
color of each pixel in a graphics buffer. data reference A reference to a media’s data.

263

G L O S S A R Y

display coordinate system The QuickDraw graphics a QuickTime movie file. This can also be called
world, which can be used to display QuickTime resolving references. Flattening is used to bring in all
movies, as opposed to the movie’s time coordinate of the data that may be referred to from multiple files
system, which defines the basic time unit for each of after QuickTime editing is complete. It makes a
the movie’s tracks. Compare time coordinate system. QuickTime movie stand-alone—that is, it can be
played on any system without requiring any
dithering A technique used to improve picture additional QuickTime movie files or tracks, even if
quality when you are attempting to display an image the original file referenced hundreds of files. The
that exists at a higher bit-depth representation on a flattening operation is essential if QuickTime movies
lower bit-depth device. For example, you might want are to be used with CD-ROM discs.
to dither a 24 bits per pixel image for display on an
8-bit screen. frame A single image in a sequence of images.

dropframe A synchronizing technique that skips frame rate The rate at which a movie is
timecodes to keep them current with video frames. displayed—that is, the number of frames per second
that are actually being displayed. In QuickTime the
duration A time interval. Durations are time values frame rate at which a movie was recorded may be
that are interpreted as spans of time, rather than as different from the frame rate at which it is displayed.
points in time. On very fast machines, the playback frame rate may
edit list A data structure that arranges a media into be faster than the record frame rate; on slow machines,
a time sequence. the playback frame rate may be slower than the record
frame rate. Frame rates may be fractional.
edit state Information defining the current state of
a movie or track with respect to an edit session. free atom An atom of type 'free', which you can
QuickTime uses edit states to support undo facilities. include in a QuickTime file as a placeholder for
unused space.
effect description A data structure that specifies
which component will be used to implement an effect graphics mode The method by which two
in a movie, and how the component will be overlapping images are blended together to produce
configured. a composite image.

effect track A modifier track that applies an effect graphics world A software environment in which
(such as a wipe or dissolve) to a movie. See modifier a movie track or set of images may be defined before
track. importing them into a movie.

file fork A section of a Macintosh file. See also data handler reference atom A QT atom of type 'hdlr'
fork, resource fork. that specifies the media handler to be used to interpret
a media. See also QT atom, media, media handler.
file preview A thumbnail picture from a movie that
is displayed in the Open File dialog box. See also hint track A track in a streaming movie that contains
thumbnail picture. information for a packetizer about the data units to
stream. See also streaming.
fixed point A point that uses fixed-point numbers
to represent its coordinates. QuickTime uses fixed hot spot An area, typically in a VR presentation, that
points to provide greater display precision for the user can click to invoke an action.
graphical and image data. hypertext Action media that contains a URL and
fixed rectangle A rectangle that uses fixed points to takes the user to a website.
represent its vertices. QuickTime uses fixed rectangles identity matrix A transformation matrix that
to provide greater display precision. specifies no change in the coordinates of the source
Flash A vector-based graphics and animation image. The resulting image corresponds exactly to the
technology. Flash data is exported by SWF files. source image. See also transformation matrix.

flattening The process of copying all of the original image In sprite programming, one of a sprite’s
data referred to by reference in QuickTime tracks into properties. See also sprite, property.

264

G L O S S A R Y

image sequence A series of visual representations numbers are displayed first; tracks with higher layer
usually represented by video over time. Image numbers are displayed over those tracks.
sequences may also be generated synthetically, such
as from an animation sequence. matrix See transformation matrix.

image track Any track in a QuickTime movie that matte A defined region of a movie display that can
contains visual images. The term particularly applies be clipped and filled with another display.
to video tracks that contain VR data. media A data structure that contains information
input map A data structure that describes where to that describes the data for a track in a movie. Note
find information about tracks that are targets of a that a media does not contain its data; rather, a media
modifier track. See modifier track. contains a reference to its data, which may be stored
on disk, CD-ROM disc, or any other mass storage
interlacing A video mode that updates half the scan device. Also called a media structure.
lines on one pass and goes through the second half
during the next pass. media handler A piece of software that is responsible
for mapping from the movie’s time coordinate system
interleaving A technique in which sound and video to the media’s time coordinate system. The media
data are alternated in small pieces, so the data can be handler also interprets the media’s data. The data
read off disk as it is needed. Interleaving allows for handler for the media is responsible for reading and
movies of almost any length with little delay on writing the media’s data. See also data handler.
startup.
MIDI Acronym for Musical Instrument Digital
ISO Acronym for the International Standards Interface, a standard format for sending instructions
Organization. ISO establishes standards for to a musical synthesizer.
multimedia data formatting and transmission, such
as JPEG and MPEG. modifier track A track in a movie that modifies the
data or presentation of other tracks. For example, a
Joint Photographic Experts Group (JPEG) Refers to tween track is a modifier track. See also tween track.
an international standard for compressing still images.
This standard supplies the algorithm for image movie A structure of time-based data that is
compression. The version of JPEG supplied with managed by QuickTime. A movie may contain sound,
QuickTime complies with the baseline ISO standard video, animation, or a combination of any of these
bitstream, version 9R9. This algorithm is best suited types of data. A QuickTime movie contains one or
for use with natural images. more tracks; each track represents a single data stream
in the movie. See also time-based data, track.
key frame A sample in a sequence of temporally
compressed samples that does not rely on other movie boundary region A region that describes the
samples in the sequence for any of its information. area occupied by a movie in the movie coordinate
Key frames are placed into temporally compressed system, before the movie has been clipped by the
sequences at a frequency that is determined by the movie clipping region. A movie’s boundary region is
key frame rate. Typically, the term key frame is used built up from the track movie boundary regions for
with respect to temporally compressed sequences of each of the movie’s tracks. See also movie clipping
image data. See also sync sample. See also key frame region, track movie boundary region.
rate. movie clipping region The clipping region of a
key frame rate The frequency with which key frames movie in the movie’s coordinate system. QuickTime
are placed into temporally compressed data sequences. applies the movie’s clipping region to the movie
See also key frame. boundary region to obtain a clipped movie boundary
region. Only that portion of the movie that lies in the
leaf atom An atom that contains only data, and no clipped movie boundary region is then transformed
other atoms. into an image in the display coordinate system. See
also movie boundary region.
layer A mechanism for prioritizing the tracks in a
movie or the overlapping of sprites. When it plays a movie display boundary region A region that
movie, QuickTime displays the movie’s tracks describes the display area occupied by a movie in the
according to their layer—tracks with lower layer display coordinate system, before the movie has been

265

G L O S S A R Y

clipped by the movie display clipping region. See also object track A track in a QuickTime VR movie that
movie display clipping region. contains a set of views of a VR object.

movie display clipping region The clipping region offset-binary encoding A method of digitally
of a movie in the display coordinate system. Only that encoding sound that represents the range of amplitude
portion of the movie that lies in the clipping region is values as an unsigned number, with the midpoint of
visible to the user. QuickTime applies the movie’s the range representing silence. For example, an 8-bit
display clipping region to the movie display boundary sound sample stored in offset-binary format would
region to obtain the visible image. See also movie contain sample values ranging from 0 to 255, with a
display boundary region. value of 128 specifying silence (no amplitude). Samples
in Macintosh sound resources are stored in
movie file A QuickTime file that stores a movie and offset-binary form. Compare twos-complement
its associated data. encoding.
movie header atom A QT atom that specifies the PAL See Phase Alternation Line (PAL).
characteristics of an entire QuickTime movie.
panorama A structure of QuickTime VR data that
movie poster A single visual image representing a forms a virtual-world environment within which the
QuickTime movie. You specify a poster as a point in user can navigate.
time in the movie and specify the tracks that are to be
used to constitute the poster image. panorama track A track in a QuickTime VR movie
that contains a panorama.
movie preview A short dynamic representation of
a QuickTime movie. Movie previews typically last no parent atom A QT atom that contains other QT
more than 3 to 5 seconds, and they should give the atoms, which are its child atoms. See also child atom.
user some idea of what the movie contains. You define
a movie preview by specifying its start time, its Phase Alternation Line (PAL) A color-encoding
duration, and its tracks. system used widely in Europe, in which one of the
subcarrier phases derived from the color burst is
movie resource One of several data structures that inverted in phase from one line to the next. This
provide the medium of exchange for movie data technique minimizes hue errors that may result during
between applications on a Macintosh computer and color video transmission. Sometimes called Phase
between computers, even computers of different types. Alternating Line.

movie sprite A sprite that lives in a sprite track and playback quality A relative measure of the fidelity
acts in a movie. See also sprite track. of a track in a QuickTime movie. You can control the
playback (or language) quality of a movie during
MPEG-4 An ISO standard (based on the QuickTime movie playback. QuickTime chooses tracks from
file format) that supports video and audio streaming. alternate tracks that most closely correspond to the
See also streaming. display quality desired. See also alternate track.
music One of the QuickTime media types, in which poster A frame shot from a movie, used to represent
sequences of sounds and tones are generated. its content to the user.
National Television System Committee preferred rate The default playback rate for a
(NTSC) Refers to the color-encoding method adopted QuickTime movie.
by the committee in 1953. This standard was the first
monochrome-compatible, simultaneous color preferred volume The default sound volume for a
transmission system used for public broadcasting. QuickTime movie.
This method is used widely in the United States.
preview A short, potentially dynamic, visual
node Either a panorama or an object in a QuickTime representation of the contents of a file. The Standard
VR movie. File Package can use previews in file dialog boxes to
give the user a visual cue about a file’s contents. See
NTSC See National Television System Committee. also file preview.

266

G L O S S A R Y

preview atom An atom of type 'pnot', which can sample format The format of data samples in a track,
appear in a QuickTime file to contain a movie’s file such as a sprite track.
preview.
sample number A number that identifies the sample
property Information about a sprite that describes with data for a specified time.
its location or appearance. One sprite property is its
image, the original bitmapped graphic of the sprite. SECAM (Systeme Electronique Couleur avec
Memoire) Sequential Color With Memory; refers to
QT atom A QuickTime atom that contains other a color-encoding system in which the red and blue
atoms, possibly including other QT atoms and classic color-difference information is transmitted on alternate
atoms. A data reference atom is an example of a QT lines, requiring a one-line memory in order to decode
atom. Compare classic atom. green information.

QTMA (QuickTime Music Architecture) The part single-fork movie file A QuickTime movie file that
of QuickTime that lets other code create and stores both the movie data and the movie resource in
manipulate music tracks in movies. the data fork of the movie file. You can use single-fork
movie files to ease the exchange of QuickTime movie
QTVR track A track in a QuickTime movie that data between Macintosh computers and other
maintains a list of VR nodes. computer systems. Compare movie file.
QuickDraw The original Mac OS two-dimensional skip atom An atom of type 'skip', which you can
drawing software, used by QuickTime. include in a QuickTime file as a placeholder for
QuickTime A set of Macintosh system extensions unused space.
or a Windows dynamic-link library that other code SMPTE Acronym for Society of Motion Picture and
can use to create and manipulate time-based data. Television Engineers, an organization that sets video
QuickTime VR A QuickTime media type that lets and movie technical standards.
users interactively explore and examine photorealistic sprite An animated image that is managed by
three-dimensional virtual worlds. QuickTime VR data QuickTime. A sprite is defined once and is then
structures are also called panoramas. animated by commands that change its position or
rate A value that specifies the pace at which time appearance.
passes for a time base. A time base’s rate is multiplied sprite track A movie track populated by movie
by the time scale to obtain the number of time units sprites.
that pass per second. For example, consider a time
base that operates in a time coordinate system that streaming Delivery of video or audio data over a
has a time scale of 60. If that time base has a rate of 1, network in real time, to support applications such as
60 time units are processed per second. If the rate is videophone and video conferencing. See MPEG-4.
set to 1/2, 30 time units pass per second. If the rate is
2, 120 time units pass per second.See also time base string atom An atom in VR media that contains text.
and time unit. SWF files Files that contain Flash data. See Flash.
resource In Macintosh programming, an entity in a sync sample A sample that does not rely on
file or in memory that may contain executable code preceding frames for content. See also key frame.
or a description of a user interface item. Resources are
loaded as needed by a resource manager, and are Systeme Electronique Couleur avec Memoire See
identified by their type and ID number. SECAM.
resource fork In a Macintosh file, the section that temporal compression Image compression that is
contains resources. performed between frames in a sequence. This
compression technique takes advantage of redundancy
root atom The largest atom container in a hierarchy, between adjacent frames in a sequence to reduce the
with atom type 'sean'. amount of data that is required to accurately represent
sample A single element of a sequence of each frame in the sequence. Sequences that have been
time-ordered data.

267

G L O S S A R Y

temporally compressed typically contain key frames track boundary region A region that describes the
at regular intervals. area occupied by a track in the track’s coordinate
system. QuickTime obtains this region by applying
thumbnail picture A picture that can be created from the track clipping region and the track matte to the
an existing image that is stored as a pixel map, a visual image contained in the track rectangle.
picture, or a picture file. A thumbnail picture is useful
for creating small representative images of a source track clipping region The clipping region of a track
image and in previews for files that contain image in the track’s coordinate system. QuickTime applies
data. the track’s clipping region and the track matte to the
image contained in the track rectangle to obtain the
time base A set of values that define the time basis track boundary region. Only that portion of the track
for an entity, such as a QuickTime movie. A time base that lies in the track boundary region is then
consists of a time coordinate system (that is, a time transformed into an image in the movie coordinate
scale and a duration) along with a rate value. The rate system.
value specifies the speed with which time passes for
the time base. track header atom A QT atom that specifies the
characteristics of a track in a QuickTime movie.
time-based data Data that changes or interacts with
the user along a time dimension. QuickTime is track height The height, in pixels, of the track
designed to handle time-based data. rectangle.

timecode media A media of type 'tmcd' that is used track input map A structure of QT atoms that
to store timecode data. specifies how secondary data for a track is to be
interpreted (clipping, blending, etc.).
timecode track A movie track that stores external
timing information, such as SMPTE timecodes. track load settings Information that specifies how
and when a track is to be preloaded before running
time coordinate system A set of values that defines in a movie.
the context for a time base. A time coordinate system
consists of a time scale and a duration. Together, these track matte A pixel map that defines the blending of
values define the coordinate system in which a time track visual data. The value of each pixel in the pixel
value or a time base has meaning. map governs the relative intensity of the track data
for the corresponding pixel in the result image.
time scale The number of time units that pass per QuickTime applies the track matte, along with the
second in a time coordinate system. A time coordinate track clipping region, to the image contained in the
system that measures time in sixtieths of a second, for track rectangle to obtain the track boundary region.
example, has a time scale of 60. See track matte, track rectangle, and track boundary
time unit The basic unit of measure for time in a time region.
coordinate system. The value of the time unit for a track movie boundary region A region that describes
time coordinate system is represented by the formula the area occupied by a track in the movie coordinate
(1/time scale) seconds. A time coordinate system that system, before the movie has been clipped by the
has a time scale of 60 measures time in terms of movie clipping region. The movie boundary region is
sixtieths of a second. built up from the track movie boundary regions for
time value A value that specifies a number of time each of the movie’s tracks.
units in a time coordinate system. A time value may track offset The blank space that represents the
contain information about a point in time or about a intervening time between the beginning of a movie
duration. and the beginning of a track’s data. In an audio track,
track A Movie Toolbox data structure that represents the blank space translates to silence; in a video track,
a single data stream in a QuickTime movie. A movie the blank space generates no visual image. All of the
may contain one or more tracks. Each track is tracks in a movie use the movie’s time coordinate
independent of other tracks in the movie and system. That is, the movie’s time scale defines the basic
represents its own data stream. Each track has a time unit for each of the movie’s tracks. Each track
corresponding media, which describes the data for begins at the beginning of the movie, but the track’s
the track.

268

G L O S S A R Y

data might not begin until some time value other than VR (virtual reality) See QuickTime VR.
0.
wired sprite A variety of sprite that acts like a
track reference A data structure that defines the button, telling other software when the user has
relation between movie tracks, such as the relation clicked on its image or passed the cursor over it.
between a timecode track and other tracks. See
timecode track.

track rectangle A rectangle that completely encloses
the visual representation of a track in a QuickTime
movie. The width of this rectangle in pixels is referred
to as the track width; the height, as the track height.

track width The width, in pixels, of the track
rectangle.

transformation matrix A 3-by-3 matrix that defines
how to map points from one coordinate space into
another coordinate space.

tween data The data in a tween track, such as
interpolation values.

tween track A modifier track that performs a specific
kind of tweening, such as path-to-matrix rotation.

tweening A process interpolating new data between
given values in conformance to an algorithm. It is an
efficient way to expand or smooth a movie’s
presentation between its actual frames.

twos-complement encoding A system for digitally
encoding sound that stores the amplitude values as a
signed number—silence is represented by a sample
with a value of 0. For example, with 8-bit sound
samples, twos-complement values would range from
–128 to 127, with 0 meaning silence. The Audio
Interchange File Format (AIFF) stores samples in
twos-complement form. Compare offset-binary
encoding.

URL The address of a website.

user data Auxiliary data that your application can
store in a QuickTime movie, track, or media structure.
The user data is stored in a user data list; items in the
list are referred to as user data items. Examples of user
data include a copyright, date of creation, name of a
movie’s director, and special hardware and software
requirements. See also user data list, user data item

user data item A single element in a user data list,
such as a modification date or copyright notice.

user data list The collection of user data for a
QuickTime movie, track, or media. Each element in
the user data list is called a user data item.

269

G L O S S A R Y

270

Index

'free' 25
Numerals 'from' 217
'gama' 96
3D media 147 'gmhd' 150
'hdlr' 58
'hdlr' 56
'hinf' 150
A 'hint' 152
'hnti' 150, 151
AddSpriteToSample function 212 'hots' 170
AddTrackReference function 146, 219 'hspa' 170
'alis' data reference type 69 'htxt' 114
APP1 marker 98 'idle' 175
'appl' data type 95 'imag' 116
application markers 98 'imap' 53
atom containers 'impn' 165
creating 208 'kmat' 46
description key 127 'link' 172
disposing of 208 'matt' 45
introduced 17 'matt' 40
samples for QTVR Flattener 239 'mdat' 19, 25
structure 22 'mdhd' 57
atom ID’s 22 'mdhd' 56
atom types 'mdia' 56
See also names of constants under K 'mdia' 40
'clik' 176 'minf' 60, 150
'clip' 40 'minf' 56
'cmov' 84 'mjht' 96
'cmvd' 84 'mjqt' 96
'crsr' 168 'moov' 25, 31, 84
'ctab' 32, 35 'moov' 29
'CURS' 168 'ndhd' 169
'dcom' 84 'nloc' 167
'dflt' 116 'pcnt' 217
'dinf' 66, 154 'pnot' 25
'dref' 68, 154 'rtp ' 151, 155
'edts' 47 'sdp ' 151
'edts' 40 'skip' 25
'elst' 48, 231 'smhd' 60
'entr' 176 'sprt' 116
'exit' 176 'ssrc' 53
'fiel' 96 'stbl' 60, 70
'fram' 175

271

I N D E X

'stco' 80 C
'stsc' 77
'stsd' 72, 153 CBR audio. See constant bit-rate audio
'stss' 75 'chap' track reference type 147
'stsz' 79 chapter lists 146
'stts' 73 child atoms
'tcmi' 109 defined 22
'tkhd' 40 finding by index 212
'trak' 32, 40 chunk offset atoms 80
'tref' 189 'clik' atom type 176
'trig' 176 'clip' atom type 32, 40
'twdt' 136 clipping atoms 44
'twdu' 136 clipping region atoms 44
'twen' 136 'cmov' atom type 84
'twnt' 136 'cmvd' atom type 84
'twst' 136 color table atoms 35
'udta' 32, 56 compressed matte atoms 46
'url ' 175 compressed movie resources 83
'vmhd' 60 constant bit-rate audio 104, 108
'vrcp' 168 container atoms 17, 22
'vrni' 167 containment hierarchy 18
'vrnp' 167 'crsr' atom type 168
'vrsc' 164 'ctab' atom type 32, 35
'vrse' 163 cubic panoramas 186
'vrsg' 163 'CURS' atom type 168
'wtxt' 114 custom atoms
siSlopeAndIntercept 104 adding to QuickTime movies 236
atom types for QTVR cursors 168
'clip' 32 for QTVR hot spots 237
atoms 'cvid' compression type 94
calculating sizes 20 cylindrical panoramas 185
child 22, 212
container 17, 22
creating 208
custom 168, 236, 237 D
IDs 22
introduction to 17 data information atoms 66
layout of 18 data reference atoms
leaf 18, 22 examples of 234
parent 22 fields in 68
audio decompression 103 date and time values 203
audio tracks, creating 226 'dcom' atom type 84
DeleteTrackReference function 146
'dflt' atom type 116
'dinf' atom type 66, 154
B 'dref' atom type 68, 154

balance values 206
base media information header atoms 64
big-endian format 243 E
edit atoms 47
edit list atoms 48, 230
'edts' atom type 40, 47

272

I N D E X

effect descriptions 215 'hnti' atom type 150, 151
'elst' atom type 48, 231 hot spot image tracks 189
EMBED tag parameters 222 hot spot information atoms 171
embedded movies 197, 222 hot spot parent atoms 170
'entr' atom type 176 hot spots in QTVR movies
'exit' atom type 176 atom types 170
external movie targets 221 sample code for intercepting 236
'hots' atom type 170
'hspa' atom type 170
'htxt' atom type 114
F Huffman tables 98
hypertext for URLs 114
'fiel' atom type 96
Flash media 135, 222
Flash media handler 222
'fram' atom type 175 I
free space atoms 25
'free' atom type 25 'idle' atom type 175
'from' atom type 217 'imag' atom type 116
image compression formats 94
image tracks
defined 176
G low-resolution 189
imaging parent atoms 165
'gama' atom type 96
'imap' atom type 53
GetMovieBoundsRgn function 145
'impn' atom type 165
'gmhd' atom type 150
input maps
graphics display operations 203
creating 217
graphics mode
updating 220
blend graphics mode 205
interleaved movie data 232
composition graphics mode 205
interpolation tween tracks 139
copy graphics mode 205
ISO JPEG specification 97
dither copy graphics mode 205
premul black alpha graphics mode 205
premul white alpha graphics mode 205
straight alpha blend graphics mode 205 J
straight alpha graphics mode 205
transparent graphics mode 205 JPEG 97
graphics modes 204 'jpeg' compression type 94

H K
handler reference atoms 58 kActionTarget atom type 222
'hdlr' atom type 56, 58 kCrossFadeTransitionType atom type 216
'hinf' atom type 150 kDVAudioFormat sound codec 107
hint media 148 kEffectDataSourceType atom type 218
hint tracks key frames 75, 82
and media tracks 152 kInitialRotationAtom atom type 141
and sample description atoms 153 kListElementType atom type 140
and track atoms 40 'kmat' atom type 46
introduced 148 kMovieMediaAltText atom type 199
user data atoms 150 kMovieMediaAutoPlay atom type 198
'hint' atom type 152 kMovieMediaBackgroundColor atom type 200

273

I N D E X

kMovieMediaClipBegin atom type 199 kSpriteStatusStringsBehaviorAtomType atom type
kMovieMediaClipDuration atom type 199 124
kMovieMediaDataReference atom type 197 kSpriteTrackPropertyHasActions atom type 121,
kMovieMediaDefaultDataReferenceID atom type 175
197 kSpriteTrackPropertyQTIdleEventsFrequency
kMovieMediaEnableFrameStepping atom type 200 atom type 121, 175
kMovieMediaRectangleAtom atom type 200 kSpriteTrackPropertyScaleSpritesToScaleWorld
kMovieMediaRegionAtom atom type 200 atom type 122
kMovieMediaSlaveAudio atom type 198 kSpriteTrackPropertyVisible atom type 122
kMovieMediaSlaveGraphicsMode atom type 198 kSpriteUsesImageIDsAtomType atom type 125
kMovieMediaSlaveTime atom type 197 kTargetParentMovie atom type 222
kMovieMediaSlaveTrackDuration atom type 198 kTargetRootMovie atom type 222
kMovieMediaTitle atom type 199 kTrackModifierInput atom type 218
kMovieMediaUseMIMEType atom type 199 kTrackModifierReference atom type 218, 219
kNameAtom atom type 141 kTrackModifierType atom type 218
kParameterWhatName atom type 215 kTween3dInitialCondition atom type 142
'kpcd' compression type 94 kTweenData atom type 139
kQDesignCompression sound codec 107 kTweenDuration atom type 139, 140
kQTEventFrameLoaded atom type 175 kTweenEntry atom type 139
kQTEventIdle atom type 175 kTweenFlags atom type 139, 141
kQTEventMouseClick atom type 176 kTweenInterpolationID atom type 139
kQTEventMouseClickEnd atom type 176 kTweenOutputMax atom type 139
kQTEventMouseClickEndTriggerButton atom type kTweenOutputMin atom type 139
176 kTweenReturnDelta atom type 141
kQTEventMouseEnter atom type 176 kTweenStartOffset atom type 139
kQTEventMouseExit atom type 176 kTweenType atom type 139, 141
kQTVRColorCursorAtomType atom type 168 kTweenType3dCameraData atom type 142
kQTVRCursorAtomType atom type 168 kTweenType3dMatrix atom type 142
kQTVRCursorParentAtomType atom type 168 kTweenType3dQuaternion atom type 142
kQTVRHotSpotAtomType atom type 170 kTweenType3dRotateAboutAxis atom type 142
kQTVRHotSpotLinkType atom type 172 kTweenType3dRotateAboutPoint atom type 142
kQTVRHotSpotParentAtomType atom type 170 kTweenType3dRotateAboutVector atom type 142
kQTVRHotSpotURLType atom type 175 kTweenType3dRotatn atom type 142
kQTVRImagingParentAtomType atom type 165 kTweenType3dScale atom type 142
kQTVRNodeHeaderAtomType atom type 169 kTweenTypePathToFixedPoint atom type 141
kQTVRNodeIDAtomType atom type 167 kTweenTypePathToMatrixRotation atom type 141
kQTVRNodeLocationAtomType atom type 167 kTweenTypePathToMatrixTranslation atom type
kQTVRNodeParentAtomType atom type 167 141
kQTVRPanoImagingAtomType atom type 165 kTweenTypePathToMatrixTranslationAndRotation
kQTVRStringAtomType atom type 163 atom type 141
kQTVRTrackRefArrayAtomType atom type 189 kTweenTypePathXtoY atom type 141
kQTVRWorldHeaderAtomType atom type 164 kTweenTypePathYtoX atom type 141
kSpriteBehaviorsAtomType atom type 124
kSpriteCursorBehaviorAtomType atom type 124
kSpriteImageBehaviorAtomType atom type 124
kSpriteImageDataRefAtomType atom type 125 L
kSpriteImageDataRefTypeAtomType atom type 125
language code values 201
kSpriteImageDefaultImageIndexAtomType atom
leaf atoms 18, 22
type 125
link hot spot atoms 172
kSpriteImageGroupIDAtomType atom type 124, 125
'link' atom type 172
kSpriteImageRegistrationAtomType atom type
low-resolution image tracks 189
124, 125

274

I N D E X

M layout of 32
movie header 33
MACE compression 108 track 40
Macromedia Flash tracks 223 track header 41
matrices 203 track matte 45
MatrixRecord structure 138 movie data atoms 26
'matt' atom type 40, 45 movie header atoms 33
'mdat' atom type 19, 25 movie media 197
'mdhd' atom type 56, 57 MPEG layer 3 codecs 108
'mdia' atom type 40, 56 MPEG media 115
media atoms 56 'mpeg' compression type 94
media data atom types 'MPEG' media type 115
3D 147 multinode movies 178
Flash 135 'musi' data type 115
hint 148 music media
modifier tracks 145 introduced 115
movie 197 sample data 115
MPEG 115 sample description 115
music 115 MyGetNodeName function 234
sound 101
sprite 116
streaming 148
text 111 N
timecode 108
'ndhd' atom type 169
track references 146
'nloc' atom type 167
tween 136
node information atom container 169
video media 94
node parent atoms 167
VR 163
nodes 178, 234
media header atoms 57
media information atoms 60
meta-data 83
mime type for QuickTime files 25 O
'minf' atom type 56, 60, 150
'mjht' atom type 96 'obje' data type 190
'mjpa' compression type 94 object image tracks 196
'mjpb' compression type 94 object tracks 176, 190, 196
'mjqt' atom type 96
modifier tracks
adding to movies 220
defined 145 P
'moov' atom type
as basic atom type 25, 29 panorama image tracks 177, 183
as part of compressed movie 84 panorama tracks 176, 180
layout of 31 panorama-imaging atoms 165
'MooV' file type 25 parent atoms 22
Motion-JPEG 'pcnt' atom type 217
format A 98 'plug' data type 221
format B 98 'pnot' atom type 25
movie atoms preview atoms 26
clipping 44
clipping region 44
color table 35
compressed matte 46

275

I N D E X

Q 'rtp ' atom type 151, 155
RTP hint tracks 155
'qd3d' data type 147
QT atom containers. See atom containers 22
QT atoms 20
QTCopyAtom function 211 S
QTCopyAtomDataToHandle function 213
sample atoms
QTCopyAtomDataToPtr function 213
introduced 69
QTCountChildrenOfType function 211
using 82
QTCreateStandardParameterDialog function 215
sample description atoms
QTDisposeAtomContainer function 208
examples of 233
QTFindChildByID function 209
introduced 72
QTFindChildByIndex function 211
sound 102
QTGetAtomTypeAndID function 213
timecode 108
QTGetNextChildType function 211
video 94
QTInsertChild function 208, 216, 219
sample size atoms 79
QTInsertChildren function 210
sample table atoms 70
QTLockContainer function 213
sample-to-chunk atoms
QTNextChildAnyType function 211
defined 77
QTRemoveAtom function 214
examples of 233
QTRemoveChildren function 214
samples
QTReplaceAtom function 211
and chunks 69
QTSetAtomData function 213
defined 69
QTSwapAtoms function 211
'sdp ' atom type 151
QTVR Flattener 238
SetSpriteData function 212
QTVR tracks 176
siDecompressorSettings atom type 103
'qtvr' media type 179
siSlopeAndIntercept atom type 104
QTVRNodeHeaderAtom structure 169
'skip' atom type 25
QTVRNodeLocationAtom structure 167
'smc ' compression type 94
QTVRObjectSampleAtom 190
'smhd' atom type 60
QTVRPanoImagingAtom structure 166
'soun' data type 59
QTVRTrackRefEntry structure 189
sound codecs 104
QTVRWorldHeaderAtom structure 165
sound media 101
QuickTime SDK 223
sound media handler 102
QuickTime VR file format 176
sound media information atoms 62
QuickTime VR movies
sound sample data 104
adding atom containers to 238
sound sample description 102
atoms in 163
SoundDescription structure 103
optimizing 238
sprite media
wired actions inn 175
introduced 116
QuickTime VR node header atoms 234
sample data 116
"video/quicktime" mime type 25
sample description 116
track format 119
tracks 118
R sprite track property atoms 121
sprite tracks 118
'raw ' compression type 94 'sprt' atom type 116
Real Time Transport Protocol 155 'sprt' media type 116
See also RTP hint tracks 'ssrc' atom type 53
RGB data 97, 206 'stbl' atom type 60, 70
'rle ' compression type 94 'stco' atom type 80
'rpza' compression type 94 streaming media 148
'rsrc' data reference type 69 string atoms 163

276

I N D E X

string encoding atom 163 sequence 144
'stsc' atom type 77 tween media
'stsd' atom type 72, 153 data 136
'stss' atom type 75 introduced 136
'stsz' atom type 79 operation 136
'stts' atom type 73 QT atom container 138
'svqi' compression type 94 sample data 136
SWF file format 223 sample description 136
sync sample atoms 75 track 136
type categories 138
type characteristics 137
type values 137
T tween tracks
defined 136
target atoms 222
modifying 139
'tcmi' atom type 109
'twen' atom type 136
text media
'twnt' atom type 136
and hypertext 114
two-dimensional transformations 203
handler 111
'twst' atom type 136
introduced 111
sample data 113
'text' media type 111 U
time values 203
time-to-sample atoms 73 'udta' atom type 32, 56
timecode media 'ulaw' compression 105
handler 108 uncompressed audio 104
information atom 109 uncompressed RGB data 97
introduced 108 uncompressed yuv2 data 97
sample data 110 'url ' atom type 175
sample description 108 'url ' data reference type 69
timecode tracks, creating 226 URL hot spot atoms 175
'tkhd' atom type 40 user data list entry types 37
'tmcd' data type 108
track atoms 40
track header atoms 41
track input map atoms 53 V
track matte atoms 45
VBR (variable bit-rate) audio 104, 108
track reference atoms 218, 229
'vide' data type 59, 94
track references 146
video media information atoms 60
'trak' atom type 32, 40
video media information header atoms 61
transfer modes. See graphics modes
video media
transformation matrices 203
data 94
'tref' atom type 189
handler 94
'trig' atom type 176
introduced 94
'twdt' atom type 136
'twdu' atom type 136
video sample data
tween atoms
introduced 96
3D 142
JPEG 97
interpolation 143
Motion-JPEG 97
introduced 138
uncompressed RGB 97
list 142
uncompressed yuv2 97
path 141
video sample descriptions
region 144

277

I N D E X

extending 96
introduced 94
video tracks, creating 225
'vmhd' atom type 60
VR media 163
VR world atom container 164
'vrcp' atom type 168
'vrni' atom type 167
'vrnp' atom type 167
'vrsc' atom type 164
'vrse' atom type 163
'vrsg' atom type 163

W
wired action grammar 129
wired actions in QTVR tracks 175
'wtxt' atom type 114

Y
yuv2 video format 97
'Yuv2' compression type 94

278

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